EN-304-617.md

**Professional Users**: Individuals using browsers for work-related activities:

- Moderate technical expertise with domain-specific knowledge
- Activities: SaaS applications, web-based productivity tools, professional research
- Subject to organizational security policies
- Generally higher security awareness due to training
- Balance productivity needs with security requirements

**Developers and Technical Users**: Advanced users with deep technical knowledge:

- High technical expertise; understand browser internals and web standards
- Activities: web development, testing, debugging, performance analysis
- Require access to developer tools and advanced features
- Higher tolerance for security friction; may disable controls intentionally
- Capable of understanding and responding to complex security warnings

**Enterprise Administrators**: IT personnel managing browser deployments:

- High technical expertise in systems administration
- Responsible for configuring, deploying, and managing browsers at scale
- Implement group policies and security configurations
- Monitor browser usage and security events
- Balance security requirements with user productivity

**Children and Protected Users**: Vulnerable populations requiring enhanced protection:

- Limited technical expertise and security awareness
- Susceptible to social engineering and inappropriate content
- Require parental controls and content filtering
- May not understand consequences of security decisions
- Need simplified security interfaces with reduced decision-making burden

### 4.8.2 User Behavior Patterns

**Security Decision-Making**: Users exhibit common patterns in security decisions:

- **Alert Fatigue**: Repeated security prompts lead to automatic dismissal without reading
- **Optimism Bias**: Underestimation of personal risk ("it won't happen to me")
- **Immediate Gratification**: Preference for immediate access over security delay
- **Trust Misplacement**: Difficulty distinguishing legitimate from malicious content
- **Habituation**: Security behaviors become routine without conscious evaluation

**Permission Granting**: When presented with permission requests, users typically:

- Grant permissions to accomplish immediate tasks without evaluating necessity
- Lack understanding of implications of granted permissions
- Rarely review or revoke previously granted permissions
- May not notice when permissions are being actively used

**Update Behavior**: User approaches to browser updates vary:

- Some users apply updates immediately when prompted
- Others defer updates indefinitely to avoid interruption
- Many users unaware of update status or importance
- Corporate environments often enforce centralized update management

### 4.8.3 User Needs and Expectations

**Usability**: Users expect browsers to be:

- Intuitive and easy to use without extensive training
- Responsive and fast, with minimal performance impact from security features
- Compatible with their required websites and applications
- Consistent across sessions and devices

**Privacy**: Users increasingly expect:

- Control over personal data collection and usage
- Protection from tracking by advertisers and third parties
- Transparency about data practices
- Compliance with privacy regulations

**Security**: While security awareness varies, users generally expect:

- Protection from malware and phishing without constant manual intervention
- Clear warnings when accessing dangerous sites
- Secure handling of passwords and payment information
- Prevention of unauthorized access to sensitive data

**Transparency**: Users need:

- Understandable explanations of security features and warnings
- Visibility into what data is being collected and shared
- Clear indication of security status (encrypted connections, permissions in use)
- Accessible security settings and controls

### 4.8.4 User Assistance and Responsibilities

**User Responsibilities**: Effective browser security requires users to:

- Keep browsers updated to address vulnerabilities
- Exercise caution with extension installation
- Recognize and avoid phishing attempts
- Use strong, unique passwords for web accounts
- Respond appropriately to security warnings
- Report security incidents when encountered

**Browser Responsibilities to Users**: Browsers shall support users by:

- Providing clear, actionable security warnings
- Using understandable language avoiding technical jargon
- Offering contextual help and explanations
- Defaulting to secure configurations
- Making security controls discoverable and accessible
- Minimizing security decision burden through sound defaults

### 4.8.5 Accessibility Considerations

Security features shall be accessible to users with disabilities:

- **Visual Impairments**: Security indicators shall be perceivable by screen readers; warnings shall not rely solely on color
- **Cognitive Disabilities**: Security messages shall be simple and clear; complex security decisions should be minimized
- **Motor Impairments**: Security controls shall be operable with alternative input methods
- **Hearing Impairments**: Audio-based security notifications shall have visual alternatives

Accessibility requirements shall not compromise security effectiveness, but security features should not exclude users with disabilities from safe browser usage.

# 5 Browser-Specific Risk Factors

### 5.1 Isolation Mechanisms

#### 5.1.1 Domain and Origin Isolation

**[DOM]** The manufacturer shall ensure that execution contexts belonging to different origins are securely isolated to prevent unauthorized data access, code execution, or state manipulation across boundaries.
Isolation shall include process separation, independent storage and cache spaces, and validation of all cross-origin communication through standardized, browser-mediated mechanisms such as Cross-Origin Resource Sharing (CORS), which allows controlled sharing of resources between origins through validated HTTP headers, and postMessage, which provides a secure message-passing interface between isolated contexts (e.g. frames or windows).
Any relaxation of isolation shall be explicitly authorized, documented, and monitored to prevent data leakage or privilege escalation.

**Capability**: Browser enforces isolation between domains and origins (defined by scheme, host, and port) to protect integrity and confidentiality of data and execution.

**Conditions**:

* DOM-0: Full isolation: Each origin is strictly separated. No mechanism exists for cross-origin access or relaxation.
* DOM-1: Controlled isolation: Isolation is enforced by default but may be selectively relaxed through standardized, browser-mediated mechanisms (e.g. CORS or postMessage) with explicit validation.
* DOM-2: Configurable isolation: Isolation is enforced by default, but users or administrators can define exceptions via explicit configuration or policy.
* DOM-3: Integrated isolation: Isolation remains in place, but third-party integrations, compatibility modes, or embedded components may introduce controlled exceptions under defined policies.

**Threats**:

- Cross-site scripting (XSS) attacks
- Cross-site request forgery (CSRF)
- Data exfiltration between origins
- Session hijacking
- Clickjacking

**Risk**: HIGH - Failure of isolation mechanisms enables immediate compromise of user data across multiple web applications

**Requirements**:

#### DOM-0 Requirements (Full isolation)

- **DOM-0-REQ-1**: Browser shall implement process-per-site isolation for all origins → Assessment: DOM-REQ-1
- **DOM-0-REQ-2**: Browser shall enforce Cross-Origin Read Blocking (CORB) for all cross-origin resource loads → Assessment: DOM-REQ-2
- **DOM-0-REQ-3**: Browser shall prevent all cross-origin DOM access without exception → Assessment: DOM-REQ-3
- **DOM-0-REQ-4**: Browser shall isolate localStorage and IndexedDB per origin with no sharing mechanism → Assessment: DOM-REQ-6
- **DOM-0-REQ-5**: Browser shall treat all sandboxed and data: origins as opaque with no relaxation → Assessment: DOM-REQ-8
- **DOM-0-REQ-6**: Browser shall enforce document.domain restrictions without any override mechanism → Assessment: DOM-REQ-12

#### DOM-1 Requirements (Controlled isolation)

- **DOM-1-REQ-1**: Browser shall implement process-per-site isolation → Assessment: DOM-REQ-1
- **DOM-1-REQ-2**: Browser shall enforce CORB with exceptions only for properly configured CORS headers → Assessment: DOM-REQ-2
- **DOM-1-REQ-3**: Browser shall prevent cross-origin DOM access except via postMessage → Assessment: DOM-REQ-3
- **DOM-1-REQ-4**: Browser shall enforce CORS preflight for all non-simple cross-origin requests → Assessment: DOM-REQ-4
- **DOM-1-REQ-5**: Browser shall enforce SameSite cookie attribute with Lax as default → Assessment: DOM-REQ-5
- **DOM-1-REQ-6**: Browser shall isolate storage per origin → Assessment: DOM-REQ-6
- **DOM-1-REQ-7**: Browser shall support iframe sandbox attribute with granular tokens → Assessment: DOM-REQ-7
- **DOM-1-REQ-8**: Browser shall treat sandboxed and data: origins as opaque → Assessment: DOM-REQ-8
- **DOM-1-REQ-9**: Browser shall restrict document.domain setter by default (require Origin-Agent-Cluster opt-out) → Assessment: DOM-REQ-12

#### DOM-2 Requirements (Configurable isolation)

- **DOM-2-REQ-1**: Browser shall implement process-per-site isolation → Assessment: DOM-REQ-1
- **DOM-2-REQ-2**: Browser shall enforce CORB → Assessment: DOM-REQ-2
- **DOM-2-REQ-3**: Browser shall prevent cross-origin DOM access except via CORS and postMessage → Assessment: DOM-REQ-3
- **DOM-2-REQ-4**: Browser shall enforce CORS preflight → Assessment: DOM-REQ-4
- **DOM-2-REQ-5**: Browser shall enforce SameSite cookie policies → Assessment: DOM-REQ-5
- **DOM-2-REQ-6**: Browser shall isolate storage per origin → Assessment: DOM-REQ-6
- **DOM-2-REQ-7**: Browser shall support iframe sandboxing → Assessment: DOM-REQ-7
- **DOM-2-REQ-8**: Browser shall support Cross-Origin-Resource-Policy (CORP) header → Assessment: DOM-REQ-9
- **DOM-2-REQ-9**: Browser shall enforce Cross-Origin-Opener-Policy (COOP) → Assessment: DOM-REQ-10
- **DOM-2-REQ-10**: Browser shall enforce Cross-Origin-Embedder-Policy (COEP) → Assessment: DOM-REQ-11
- **DOM-2-REQ-11**: Administrators shall be able to configure origin isolation policies via enterprise policy
- **DOM-2-REQ-12**: Browser shall log all policy-based isolation exceptions

#### DOM-3 Requirements (Integrated isolation)

- **DOM-3-REQ-1**: Browser shall implement baseline process-per-site isolation → Assessment: DOM-REQ-1
- **DOM-3-REQ-2**: Browser shall enforce CORB with documented exceptions for compatibility → Assessment: DOM-REQ-2
- **DOM-3-REQ-3**: Browser shall enforce CORS policies → Assessment: DOM-REQ-4
- **DOM-3-REQ-4**: Browser shall enforce SameSite cookie policies → Assessment: DOM-REQ-5
- **DOM-3-REQ-5**: Browser shall isolate storage per origin → Assessment: DOM-REQ-6
- **DOM-3-REQ-6**: Browser shall support CORP, COOP, and COEP headers → Assessments: DOM-REQ-9, DOM-REQ-10, DOM-REQ-11
- **DOM-3-REQ-7**: Compatibility modes shall not weaken core isolation boundaries
- **DOM-3-REQ-8**: Third-party integrations shall be subject to same origin isolation policies
- **DOM-3-REQ-9**: All isolation exceptions for compatibility shall be documented and logged
- **DOM-3-REQ-10**: Embedded components shall maintain storage isolation from embedding context

### 5.2 Extension System Security

#### 5.2.1 Third-Party Code Execution

**[EXT]** The manufacturer shall implement controls for third-party extensions that can modify browser behavior, considering that certified extensions may still exhibit malicious behavior.

**Capability**: Browser extension system with APIs for third-party code augmentation

**Conditions**:

- EXT-0: No extension support
- EXT-1: Curated extension store only
- EXT-2: Curated store with developer mode
- EXT-3: Unrestricted extension installation

**Threats**:

- Malicious extensions harvesting user data
- Extension-based cryptomining
- Browser fingerprinting
- Privilege escalation through extension APIs
- Supply chain attacks on popular extensions

**Risk**: HIGH - Extensions operate as semi-trusted code with significant access to browser functionality and user data

**Requirements**:

#### EXT-0 Requirements (No extension support)

- **EXT-0-REQ-1**: Browser shall not provide any extension installation or execution capability
- **EXT-0-REQ-2**: Browser shall block all attempts to load extension code
- **EXT-0-REQ-3**: Browser build shall not include extension subsystem components

#### EXT-1 Requirements (Curated extension store only)

- **EXT-1-REQ-1**: Browser shall implement granular permission model for extensions → Assessment: EXT-REQ-1
- **EXT-1-REQ-2**: Browser shall isolate extension content scripts from page scripts → Assessment: EXT-REQ-2
- **EXT-1-REQ-3**: Browser shall enforce extension API access control based on declared permissions → Assessment: EXT-REQ-3
- **EXT-1-REQ-4**: Browser shall validate extension manifests before installation → Assessment: EXT-REQ-4
- **EXT-1-REQ-5**: Browser shall sandbox extension execution environments → Assessment: EXT-REQ-5
- **EXT-1-REQ-6**: Browser shall isolate extensions from each other → Assessment: EXT-REQ-6
- **EXT-1-REQ-7**: Browser shall validate host permissions against declared patterns → Assessment: EXT-REQ-7
- **EXT-1-REQ-8**: Browser shall enforce Content Security Policy for extensions → Assessment: EXT-REQ-8
- **EXT-1-REQ-9**: Browser shall verify extension update signatures from official store → Assessment: EXT-REQ-10
- **EXT-1-REQ-10**: Browser shall enforce Manifest V3 compliance for new extensions → Assessment: EXT-REQ-13
- **EXT-1-REQ-11**: Browser shall validate extension signatures before installation → Assessment: EXT-REQ-17
- **EXT-1-REQ-12**: Browser shall provide transparent permissions UI during installation → Assessment: EXT-REQ-18
- **EXT-1-REQ-13**: Browser shall only allow installation from official curated store
- **EXT-1-REQ-14**: Extensions shall undergo security review before store publication

#### EXT-2 Requirements (Curated store with developer mode)

- **EXT-2-REQ-1**: Browser shall implement all EXT-1 requirements for store-installed extensions
- **EXT-2-REQ-2**: Browser shall isolate extension storage per extension → Assessment: EXT-REQ-11
- **EXT-2-REQ-3**: Browser shall restrict background script capabilities → Assessment: EXT-REQ-12
- **EXT-2-REQ-4**: Browser shall enforce WebRequest API security controls → Assessment: EXT-REQ-9
- **EXT-2-REQ-5**: Browser shall monitor extension-controlled web content → Assessment: EXT-REQ-15
- **EXT-2-REQ-6**: Developer mode shall require explicit user activation with security warnings
- **EXT-2-REQ-7**: Developer mode extensions shall display persistent visual indicators
- **EXT-2-REQ-8**: Developer mode shall disable automatic extension updates
- **EXT-2-REQ-9**: Browser shall log all developer mode extension activities
- **EXT-2-REQ-10**: Enterprise policies shall be able to disable developer mode

#### EXT-3 Requirements (Unrestricted extension installation)

- **EXT-3-REQ-1**: Browser shall implement baseline extension permission model → Assessment: EXT-REQ-1
- **EXT-3-REQ-2**: Browser shall enforce content script isolation → Assessment: EXT-REQ-2
- **EXT-3-REQ-3**: Browser shall control extension API access → Assessment: EXT-REQ-3
- **EXT-3-REQ-4**: Browser shall validate extension manifests → Assessment: EXT-REQ-4
- **EXT-3-REQ-5**: Browser shall sandbox extensions → Assessment: EXT-REQ-5
- **EXT-3-REQ-6**: Browser shall isolate extensions from each other → Assessment: EXT-REQ-6
- **EXT-3-REQ-7**: Browser shall enforce native messaging security controls → Assessment: EXT-REQ-14
- **EXT-3-REQ-8**: Browser shall monitor extension telemetry with privacy protections → Assessment: EXT-REQ-16
- **EXT-3-REQ-9**: Sideloaded extensions shall display prominent security warnings
- **EXT-3-REQ-10**: Browser shall provide user controls to review and revoke extension permissions
- **EXT-3-REQ-11**: Browser shall scan sideloaded extensions for known malware signatures
- **EXT-3-REQ-12**: All extension security events shall be logged for review

### 5.3 Encryption Implementation

#### 5.3.1 Data Protection Layers

**[ENC]** The manufacturer shall implement comprehensive encryption across all data states and communication channels.

**Capability**: Multi-layer encryption for data in transit, at rest, and during synchronization

**Conditions**:

- ENC-0: Full encryption with hardware security module support
- ENC-1: Standard encryption with software-based key management
- ENC-2: Selective encryption based on data sensitivity
- ENC-3: Basic encryption with user-optional enhanced protection
- ENC-4: Full

**Threats**:

- Man-in-the-middle attacks
- Data breach of stored credentials
- Synchronization data interception
- Update channel compromise
- Certificate validation bypass

**Risk**: CRITICAL - Encryption failures expose all user data and communications

**Requirements**:

#### ENC-0 Requirements (Full encryption with HSM support)

- **ENC-0-REQ-1**: Browser shall support TLS 1.3 or higher exclusively for all network communications → Assessment: ENC-REQ-1
- **ENC-0-REQ-2**: Browser shall perform complete certificate chain validation including expiry, revocation, and trust anchor verification → Assessment: ENC-REQ-2
- **ENC-0-REQ-3**: Browser shall enforce HTTP Public Key Pinning (HPKP) or alternative certificate pinning mechanisms → Assessment: ENC-REQ-3
- **ENC-0-REQ-4**: Browser shall enforce HTTP Strict Transport Security (HSTS) with preload support → Assessment: ENC-REQ-4
- **ENC-0-REQ-5**: Browser shall block all mixed content without exception → Assessment: ENC-REQ-5
- **ENC-0-REQ-6**: Browser shall enforce Certificate Transparency requirements for all certificates → Assessment: ENC-REQ-6
- **ENC-0-REQ-7**: Browser shall support and validate OCSP stapling responses → Assessment: ENC-REQ-7
- **ENC-0-REQ-8**: Browser shall restrict cipher suites to strong, modern algorithms only → Assessment: ENC-REQ-8
- **ENC-0-REQ-9**: Browser shall enforce perfect forward secrecy for all TLS connections → Assessment: ENC-REQ-9
- **ENC-0-REQ-10**: Browser shall perform real-time certificate revocation checking → Assessment: ENC-REQ-10
- **ENC-0-REQ-11**: Browser shall implement Web Crypto API with full W3C compliance → Assessment: ENC-REQ-11
- **ENC-0-REQ-12**: Browser shall provide cryptographically secure random number generation → Assessment: ENC-REQ-12
- **ENC-0-REQ-13**: Browser shall enforce SubResource Integrity (SRI) validation → Assessment: ENC-REQ-13
- **ENC-0-REQ-14**: Browser shall support Encrypted SNI (ESNI) or Encrypted Client Hello (ECH) → Assessment: ENC-REQ-14
- **ENC-0-REQ-15**: Browser shall display prominent, non-bypassable certificate error UI → Assessment: ENC-REQ-15
- **ENC-0-REQ-16**: Browser shall operate in HTTPS-first mode with automatic upgrade → Assessment: ENC-REQ-16
- **ENC-0-REQ-17**: Browser shall detect and alert on certificate pinning bypass attempts → Assessment: ENC-REQ-17
- **ENC-0-REQ-18**: Browser shall protect against TLS downgrade attacks → Assessment: ENC-REQ-18
- **ENC-0-REQ-19**: Browser shall deprecate and disable legacy cryptographic protocols (SSL, TLS 1.0/1.1) → Assessment: ENC-REQ-19
- **ENC-0-REQ-20**: Browser shall isolate cryptographic keys in hardware security modules when available → Assessment: ENC-REQ-20
- **ENC-0-REQ-21**: Browser shall implement secure certificate store with integrity protection → Assessment: ENC-REQ-21
- **ENC-0-REQ-22**: Browser shall not allow user override of certificate pinning failures
- **ENC-0-REQ-23**: All cryptographic operations shall be performed in hardware-backed secure enclaves when available

#### ENC-1 Requirements (Standard encryption with software key management)

- **ENC-1-REQ-1**: Browser shall support TLS 1.3 or higher for all network communications → Assessment: ENC-REQ-1
- **ENC-1-REQ-2**: Browser shall perform complete certificate chain validation → Assessment: ENC-REQ-2
- **ENC-1-REQ-3**: Browser shall support certificate pinning mechanisms → Assessment: ENC-REQ-3
- **ENC-1-REQ-4**: Browser shall enforce HSTS to prevent protocol downgrade attacks → Assessment: ENC-REQ-4
- **ENC-1-REQ-5**: Browser shall block mixed content with opt-in for passive content → Assessment: ENC-REQ-5
- **ENC-1-REQ-6**: Browser shall validate Certificate Transparency logs → Assessment: ENC-REQ-6
- **ENC-1-REQ-7**: Browser shall support OCSP stapling → Assessment: ENC-REQ-7
- **ENC-1-REQ-8**: Browser shall restrict cipher suites to industry-standard secure algorithms → Assessment: ENC-REQ-8
- **ENC-1-REQ-9**: Browser shall prefer perfect forward secrecy cipher suites → Assessment: ENC-REQ-9
- **ENC-1-REQ-10**: Browser shall perform certificate revocation checking (OCSP or CRLSets) → Assessment: ENC-REQ-10
- **ENC-1-REQ-11**: Browser shall implement Web Crypto API → Assessment: ENC-REQ-11
- **ENC-1-REQ-12**: Browser shall provide secure random number generation → Assessment: ENC-REQ-12
- **ENC-1-REQ-13**: Browser shall support SubResource Integrity validation → Assessment: ENC-REQ-13
- **ENC-1-REQ-14**: Browser shall display clear certificate error UI with bypass warnings → Assessment: ENC-REQ-15
- **ENC-1-REQ-15**: Browser shall support HTTPS-first mode as user option → Assessment: ENC-REQ-16
- **ENC-1-REQ-16**: Browser shall protect against TLS downgrade attacks → Assessment: ENC-REQ-18
- **ENC-1-REQ-17**: Browser shall disable legacy cryptographic protocols by default → Assessment: ENC-REQ-19
- **ENC-1-REQ-18**: Browser shall isolate cryptographic keys in process-level sandboxes → Assessment: ENC-REQ-20
- **ENC-1-REQ-19**: Browser shall implement secure certificate store → Assessment: ENC-REQ-21

#### ENC-2 Requirements (Selective encryption)

- **ENC-2-REQ-1**: Browser shall support TLS 1.3 and TLS 1.2 → Assessment: ENC-REQ-1
- **ENC-2-REQ-2**: Browser shall perform certificate chain validation → Assessment: ENC-REQ-2
- **ENC-2-REQ-3**: Browser shall support certificate pinning for critical domains → Assessment: ENC-REQ-3
- **ENC-2-REQ-4**: Browser shall enforce HSTS when declared by server → Assessment: ENC-REQ-4
- **ENC-2-REQ-5**: Browser shall warn about mixed content → Assessment: ENC-REQ-5
- **ENC-2-REQ-6**: Browser shall support Certificate Transparency → Assessment: ENC-REQ-6
- **ENC-2-REQ-7**: Browser shall support OCSP stapling → Assessment: ENC-REQ-7
- **ENC-2-REQ-8**: Browser shall support standard cipher suites → Assessment: ENC-REQ-8
- **ENC-2-REQ-9**: Browser shall support forward secrecy cipher suites → Assessment: ENC-REQ-9
- **ENC-2-REQ-10**: Browser shall perform revocation checking with soft-fail option → Assessment: ENC-REQ-10
- **ENC-2-REQ-11**: Browser shall implement Web Crypto API → Assessment: ENC-REQ-11
- **ENC-2-REQ-12**: Browser shall provide secure random number generation → Assessment: ENC-REQ-12
- **ENC-2-REQ-13**: Browser shall support SubResource Integrity → Assessment: ENC-REQ-13
- **ENC-2-REQ-14**: Browser shall display certificate errors with bypass option → Assessment: ENC-REQ-15
- **ENC-2-REQ-15**: Browser shall provide HTTPS upgrade suggestions → Assessment: ENC-REQ-16
- **ENC-2-REQ-16**: Browser shall maintain secure certificate store → Assessment: ENC-REQ-21
- **ENC-2-REQ-17**: Users shall be able to configure encryption strictness levels
- **ENC-2-REQ-18**: Browser shall provide visual indicators for connection security status

#### ENC-3 Requirements (Basic encryption with optional enhanced protection)

- **ENC-3-REQ-1**: Browser shall support TLS 1.2 or higher → Assessment: ENC-REQ-1
- **ENC-3-REQ-2**: Browser shall perform basic certificate validation → Assessment: ENC-REQ-2
- **ENC-3-REQ-3**: Browser shall enforce HSTS when enabled → Assessment: ENC-REQ-4
- **ENC-3-REQ-4**: Browser shall notify users of mixed content → Assessment: ENC-REQ-5
- **ENC-3-REQ-5**: Browser shall support common cipher suites → Assessment: ENC-REQ-8
- **ENC-3-REQ-6**: Browser shall support certificate revocation checking → Assessment: ENC-REQ-10
- **ENC-3-REQ-7**: Browser shall implement Web Crypto API → Assessment: ENC-REQ-11
- **ENC-3-REQ-8**: Browser shall provide secure random number generation → Assessment: ENC-REQ-12
- **ENC-3-REQ-9**: Browser shall display certificate errors with clear bypass options → Assessment: ENC-REQ-15
- **ENC-3-REQ-10**: Browser shall support basic certificate store operations → Assessment: ENC-REQ-21
- **ENC-3-REQ-11**: Users shall have full control over encryption settings
- **ENC-3-REQ-12**: Browser shall provide encryption status indicators in UI
- **ENC-3-REQ-13**: Legacy protocol support may be enabled for compatibility with user consent

#### ENC-4 Requirements (Minimal encryption)

- **ENC-4-REQ-1**: Browser shall support TLS 1.2 → Assessment: ENC-REQ-1
- **ENC-4-REQ-2**: Browser shall perform basic certificate validation → Assessment: ENC-REQ-2
- **ENC-4-REQ-3**: Browser shall display certificate warnings → Assessment: ENC-REQ-15
- **ENC-4-REQ-4**: Browser shall implement Web Crypto API for web applications → Assessment: ENC-REQ-11
- **ENC-4-REQ-5**: Browser shall provide secure random number generation → Assessment: ENC-REQ-12
- **ENC-4-REQ-6**: Users shall have complete control over all encryption policies
- **ENC-4-REQ-7**: Browser shall support legacy protocols when explicitly enabled by user

### 5.4 Diagnostic and Monitoring Systems

#### 5.4.1 Logging and Crash Reporting

**[LOG]** The manufacturer shall balance diagnostic capabilities with privacy protection in logging and monitoring systems.

**Capability**: Crash dumps, audit trails, activity logs, and enterprise integration capabilities

**Conditions**:

- LOG-0: No logging or local-only logging
- LOG-1: Opt-in telemetry with anonymization
- LOG-2: Default telemetry with opt-out
- LOG-3: Mandatory telemetry for enterprise management

**Threats**:

- Information disclosure through logs
- Privacy violations via telemetry
- Log tampering or deletion
- Unauthorized access to diagnostic data
- Correlation attacks using telemetry data

**Risk**: MEDIUM - Diagnostic systems may leak sensitive information while being necessary for security monitoring

**Requirements**:

#### LOG-0 Requirements (No logging or local-only)

- **LOG-0-REQ-1**: Browser shall not transmit any telemetry or diagnostic data to remote servers
- **LOG-0-REQ-2**: Browser shall maintain local security event logs for audit purposes → Assessment: LOG-REQ-1
- **LOG-0-REQ-3**: Local logs shall be stored with integrity protection → Assessment: LOG-REQ-11
- **LOG-0-REQ-4**: Local logs shall implement data minimization principles → Assessment: LOG-REQ-7
- **LOG-0-REQ-5**: Browser shall provide local security dashboard for log review → Assessment: LOG-REQ-13
- **LOG-0-REQ-6**: Local logs shall support forensic export for security analysis → Assessment: LOG-REQ-17
- **LOG-0-REQ-7**: Browser shall enforce strict access controls on local log files → Assessment: LOG-REQ-20
- **LOG-0-REQ-8**: All logging shall be disabled by default with opt-in for local logging
- **LOG-0-REQ-9**: Users shall be able to view and delete all local logs at any time

#### LOG-1 Requirements (Opt-in telemetry with anonymization)

- **LOG-1-REQ-1**: Browser shall log security events locally → Assessment: LOG-REQ-1
- **LOG-1-REQ-2**: Browser shall log certificate errors and validation failures → Assessment: LOG-REQ-2
- **LOG-1-REQ-3**: Browser shall log extension security events → Assessment: LOG-REQ-3
- **LOG-1-REQ-4**: Browser shall support CSP violation reporting → Assessment: LOG-REQ-4
- **LOG-1-REQ-5**: Browser shall support Network Error Logging (NEL) → Assessment: LOG-REQ-5
- **LOG-1-REQ-6**: Browser shall implement crash reporting with user consent → Assessment: LOG-REQ-6
- **LOG-1-REQ-7**: Browser shall minimize data collection in logs → Assessment: LOG-REQ-7
- **LOG-1-REQ-8**: Browser shall anonymize telemetry data before transmission → Assessment: LOG-REQ-8
- **LOG-1-REQ-9**: Browser shall require explicit user consent for all telemetry → Assessment: LOG-REQ-9
- **LOG-1-REQ-10**: Browser shall transmit logs over secure channels only → Assessment: LOG-REQ-10
- **LOG-1-REQ-11**: Browser shall protect log integrity with cryptographic signatures → Assessment: LOG-REQ-11
- **LOG-1-REQ-12**: Browser shall enforce log retention policies → Assessment: LOG-REQ-12
- **LOG-1-REQ-13**: Browser shall provide security dashboard for log review → Assessment: LOG-REQ-13
- **LOG-1-REQ-14**: Browser shall use privacy-preserving analytics techniques → Assessment: LOG-REQ-18
- **LOG-1-REQ-15**: Browser shall enforce access controls on diagnostic data → Assessment: LOG-REQ-20
- **LOG-1-REQ-16**: Telemetry shall be disabled by default and require explicit opt-in
- **LOG-1-REQ-17**: Users shall have granular control over telemetry categories
- **LOG-1-REQ-18**: Browser shall provide clear documentation of all collected data

#### LOG-2 Requirements (Default telemetry with opt-out)

- **LOG-2-REQ-1**: Browser shall log security events → Assessment: LOG-REQ-1
- **LOG-2-REQ-2**: Browser shall log certificate errors → Assessment: LOG-REQ-2
- **LOG-2-REQ-3**: Browser shall log extension security events → Assessment: LOG-REQ-3
- **LOG-2-REQ-4**: Browser shall support CSP violation reporting → Assessment: LOG-REQ-4
- **LOG-2-REQ-5**: Browser shall support Network Error Logging → Assessment: LOG-REQ-5
- **LOG-2-REQ-6**: Browser shall implement crash reporting → Assessment: LOG-REQ-6
- **LOG-2-REQ-7**: Browser shall minimize logged data → Assessment: LOG-REQ-7
- **LOG-2-REQ-8**: Browser shall anonymize telemetry data → Assessment: LOG-REQ-8
- **LOG-2-REQ-9**: Browser shall provide clear opt-out mechanism during first run → Assessment: LOG-REQ-9
- **LOG-2-REQ-10**: Browser shall transmit logs securely → Assessment: LOG-REQ-10
- **LOG-2-REQ-11**: Browser shall protect log integrity → Assessment: LOG-REQ-11
- **LOG-2-REQ-12**: Browser shall enforce retention policies → Assessment: LOG-REQ-12
- **LOG-2-REQ-13**: Browser shall provide security dashboard → Assessment: LOG-REQ-13
- **LOG-2-REQ-14**: Browser shall support incident detection → Assessment: LOG-REQ-14
- **LOG-2-REQ-15**: Browser shall maintain complete audit trail → Assessment: LOG-REQ-15
- **LOG-2-REQ-16**: Browser shall use privacy-preserving analytics → Assessment: LOG-REQ-18
- **LOG-2-REQ-17**: Browser shall support compliance logging → Assessment: LOG-REQ-19
- **LOG-2-REQ-18**: Browser shall enforce log access controls → Assessment: LOG-REQ-20
- **LOG-2-REQ-19**: Users shall be able to disable telemetry at any time
- **LOG-2-REQ-20**: Browser shall display telemetry status in settings UI

#### LOG-3 Requirements (Mandatory telemetry for enterprise)

- **LOG-3-REQ-1**: Browser shall log all security events → Assessment: LOG-REQ-1
- **LOG-3-REQ-2**: Browser shall log certificate errors and security warnings → Assessment: LOG-REQ-2
- **LOG-3-REQ-3**: Browser shall log all extension security events → Assessment: LOG-REQ-3
- **LOG-3-REQ-4**: Browser shall support CSP violation reporting → Assessment: LOG-REQ-4
- **LOG-3-REQ-5**: Browser shall support Network Error Logging → Assessment: LOG-REQ-5
- **LOG-3-REQ-6**: Browser shall implement comprehensive crash reporting → Assessment: LOG-REQ-6
- **LOG-3-REQ-7**: Browser shall log data with minimal redaction for forensics → Assessment: LOG-REQ-7
- **LOG-3-REQ-8**: Browser shall transmit logs securely to enterprise SIEM → Assessment: LOG-REQ-10
- **LOG-3-REQ-9**: Browser shall protect log integrity with cryptographic controls → Assessment: LOG-REQ-11
- **LOG-3-REQ-10**: Browser shall enforce enterprise-defined retention policies → Assessment: LOG-REQ-12
- **LOG-3-REQ-11**: Browser shall provide comprehensive security dashboard → Assessment: LOG-REQ-13
- **LOG-3-REQ-12**: Browser shall support real-time incident detection → Assessment: LOG-REQ-14
- **LOG-3-REQ-13**: Browser shall maintain complete audit trail of all security events → Assessment: LOG-REQ-15
- **LOG-3-REQ-14**: Browser shall support real-time security alerts → Assessment: LOG-REQ-16
- **LOG-3-REQ-15**: Browser shall support forensic log export in standard formats → Assessment: LOG-REQ-17
- **LOG-3-REQ-16**: Browser shall implement compliance logging for regulatory requirements → Assessment: LOG-REQ-19
- **LOG-3-REQ-17**: Browser shall enforce role-based access controls for logs → Assessment: LOG-REQ-20
- **LOG-3-REQ-18**: Enterprise policies shall prevent users from disabling mandatory logging
- **LOG-3-REQ-19**: Browser shall support integration with enterprise monitoring systems
- **LOG-3-REQ-20**: Browser shall provide tamper-evident logging mechanisms

### 5.5 Update Delivery Mechanisms

#### 5.5.1 Security Update Management

**[UPD]** The manufacturer shall implement secure update mechanisms that balance security needs with user autonomy.

**Capability**: Automatic security updates with user notification and control options

**Conditions**:

- UPD-0: Forced automatic updates without user control
- UPD-1: Automatic updates with postponement options
- UPD-2: Optional automatic updates (user should enable)
- UPD-3: Manual updates only

**Threats**:

- Exploitation of unpatched vulnerabilities
- Update channel compromise
- Malicious update injection
- Denial of service through forced updates
- Zero-day exploitation window

**Risk**: HIGH - Delayed or compromised updates leave browsers vulnerable to known exploits

**Requirements**:

#### UPD-0 Requirements (Forced automatic updates)

- **UPD-0-REQ-1**: Browser shall implement automatic update mechanism without user control → Assessment: UPD-REQ-1
- **UPD-0-REQ-2**: Browser shall verify digital signatures on all updates → Assessment: UPD-REQ-2
- **UPD-0-REQ-3**: Browser shall deliver updates exclusively over HTTPS → Assessment: UPD-REQ-3
- **UPD-0-REQ-4**: Browser shall validate update manifest integrity → Assessment: UPD-REQ-4
- **UPD-0-REQ-5**: Browser shall implement rollback protection to prevent downgrade attacks → Assessment: UPD-REQ-5
- **UPD-0-REQ-6**: Browser shall isolate update channels (stable, beta, dev) → Assessment: UPD-REQ-6
- **UPD-0-REQ-7**: Browser shall support component-level updates for security patches → Assessment: UPD-REQ-7
- **UPD-0-REQ-8**: Browser shall support emergency update capability for zero-day threats → Assessment: UPD-REQ-8
- **UPD-0-REQ-9**: Browser shall verify updates before installation → Assessment: UPD-REQ-9
- **UPD-0-REQ-10**: Browser shall implement failure recovery for failed updates → Assessment: UPD-REQ-10
- **UPD-0-REQ-11**: Browser shall log all updates to transparency log → Assessment: UPD-REQ-11
- **UPD-0-REQ-12**: Browser shall validate delta update security → Assessment: UPD-REQ-12
- **UPD-0-REQ-13**: Browser shall authenticate update servers with certificate pinning → Assessment: UPD-REQ-13
- **UPD-0-REQ-14**: Browser shall implement timing jitter to prevent fingerprinting → Assessment: UPD-REQ-14
- **UPD-0-REQ-15**: Browser shall enforce background update installation → Assessment: UPD-REQ-15
- **UPD-0-REQ-16**: Browser shall force critical security updates immediately → Assessment: UPD-REQ-17
- **UPD-0-REQ-17**: Browser shall verify complete update verification chain → Assessment: UPD-REQ-18
- **UPD-0-REQ-18**: Browser shall implement update source pinning → Assessment: UPD-REQ-19
- **UPD-0-REQ-19**: Browser shall verify update integrity with cryptographic hashes → Assessment: UPD-REQ-20
- **UPD-0-REQ-20**: Browser shall support staged rollout for risk mitigation → Assessment: UPD-REQ-21
- **UPD-0-REQ-21**: Browser shall validate update domain authenticity → Assessment: UPD-REQ-22
- **UPD-0-REQ-22**: Browser shall support binary reproducibility verification → Assessment: UPD-REQ-23
- **UPD-0-REQ-23**: Updates shall be applied without user intervention or postponement
- **UPD-0-REQ-24**: Browser shall restart automatically after critical updates when safe

#### UPD-1 Requirements (Automatic with postponement)

- **UPD-1-REQ-1**: Browser shall implement automatic update mechanism → Assessment: UPD-REQ-1
- **UPD-1-REQ-2**: Browser shall verify update signatures → Assessment: UPD-REQ-2
- **UPD-1-REQ-3**: Browser shall deliver updates over HTTPS only → Assessment: UPD-REQ-3
- **UPD-1-REQ-4**: Browser shall validate update manifest integrity → Assessment: UPD-REQ-4
- **UPD-1-REQ-5**: Browser shall implement rollback protection → Assessment: UPD-REQ-5
- **UPD-1-REQ-6**: Browser shall isolate update channels → Assessment: UPD-REQ-6
- **UPD-1-REQ-7**: Browser shall support component updates → Assessment: UPD-REQ-7
- **UPD-1-REQ-8**: Browser shall support emergency updates → Assessment: UPD-REQ-8
- **UPD-1-REQ-9**: Browser shall verify updates before installation → Assessment: UPD-REQ-9
- **UPD-1-REQ-10**: Browser shall implement update failure recovery → Assessment: UPD-REQ-10
- **UPD-1-REQ-11**: Browser shall log updates to transparency log → Assessment: UPD-REQ-11
- **UPD-1-REQ-12**: Browser shall secure delta updates → Assessment: UPD-REQ-12
- **UPD-1-REQ-13**: Browser shall authenticate update servers → Assessment: UPD-REQ-13
- **UPD-1-REQ-14**: Browser shall implement update timing jitter → Assessment: UPD-REQ-14
- **UPD-1-REQ-15**: Browser shall enforce background updates → Assessment: UPD-REQ-15
- **UPD-1-REQ-16**: Browser shall display clear update notifications → Assessment: UPD-REQ-16
- **UPD-1-REQ-17**: Browser shall force critical updates with limited postponement → Assessment: UPD-REQ-17
- **UPD-1-REQ-18**: Browser shall verify update verification chain → Assessment: UPD-REQ-18
- **UPD-1-REQ-19**: Browser shall implement update source pinning → Assessment: UPD-REQ-19
- **UPD-1-REQ-20**: Browser shall verify update integrity → Assessment: UPD-REQ-20
- **UPD-1-REQ-21**: Browser shall support staged rollouts → Assessment: UPD-REQ-21
- **UPD-1-REQ-22**: Browser shall validate update domains → Assessment: UPD-REQ-22
- **UPD-1-REQ-23**: Users shall be able to postpone non-critical updates for limited time (max 7 days)
- **UPD-1-REQ-24**: Critical security updates shall not be postponable beyond 24 hours
- **UPD-1-REQ-25**: Browser shall notify users of pending updates with severity indication

#### UPD-2 Requirements (Optional automatic updates)

- **UPD-2-REQ-1**: Browser shall support automatic update mechanism when enabled → Assessment: UPD-REQ-1
- **UPD-2-REQ-2**: Browser shall verify update signatures → Assessment: UPD-REQ-2
- **UPD-2-REQ-3**: Browser shall deliver updates over HTTPS → Assessment: UPD-REQ-3
- **UPD-2-REQ-4**: Browser shall validate update manifest integrity → Assessment: UPD-REQ-4
- **UPD-2-REQ-5**: Browser shall implement rollback protection → Assessment: UPD-REQ-5
- **UPD-2-REQ-6**: Browser shall isolate update channels → Assessment: UPD-REQ-6
- **UPD-2-REQ-7**: Browser shall support component updates → Assessment: UPD-REQ-7
- **UPD-2-REQ-8**: Browser shall verify updates before installation → Assessment: UPD-REQ-9
- **UPD-2-REQ-9**: Browser shall implement update failure recovery → Assessment: UPD-REQ-10
- **UPD-2-REQ-10**: Browser shall authenticate update servers → Assessment: UPD-REQ-13
- **UPD-2-REQ-11**: Browser shall display update notifications → Assessment: UPD-REQ-16
- **UPD-2-REQ-12**: Browser shall verify update integrity → Assessment: UPD-REQ-20
- **UPD-2-REQ-13**: Browser shall validate update domains → Assessment: UPD-REQ-22
- **UPD-2-REQ-14**: Automatic updates shall be disabled by default
- **UPD-2-REQ-15**: Browser shall prominently recommend enabling automatic updates
- **UPD-2-REQ-16**: Browser shall display security warnings when updates are available
- **UPD-2-REQ-17**: Browser shall provide easy mechanism to check for and install updates
- **UPD-2-REQ-18**: Users shall have full control over update timing and installation

#### UPD-3 Requirements (Manual updates only)

- **UPD-3-REQ-1**: Browser shall verify update signatures when manually triggered → Assessment: UPD-REQ-2
- **UPD-3-REQ-2**: Browser shall deliver updates over HTTPS → Assessment: UPD-REQ-3
- **UPD-3-REQ-3**: Browser shall validate update manifest integrity → Assessment: UPD-REQ-4
- **UPD-3-REQ-4**: Browser shall implement rollback protection → Assessment: UPD-REQ-5
- **UPD-3-REQ-5**: Browser shall verify updates before installation → Assessment: UPD-REQ-9
- **UPD-3-REQ-6**: Browser shall implement update failure recovery → Assessment: UPD-REQ-10
- **UPD-3-REQ-7**: Browser shall authenticate update servers → Assessment: UPD-REQ-13
- **UPD-3-REQ-8**: Browser shall display update availability notifications → Assessment: UPD-REQ-16
- **UPD-3-REQ-9**: Browser shall verify update integrity → Assessment: UPD-REQ-20
- **UPD-3-REQ-10**: Browser shall validate update domains → Assessment: UPD-REQ-22
- **UPD-3-REQ-11**: Browser shall provide manual update check mechanism
- **UPD-3-REQ-12**: Browser shall display security warnings for outdated versions
- **UPD-3-REQ-13**: Browser shall provide clear indication of available security updates
- **UPD-3-REQ-14**: All updates shall require explicit user initiation
- **UPD-3-REQ-15**: Browser shall display update changelog and security impact

### 5.6 Protocol Handler Security

#### 5.6.1 Custom Protocol Management

**[PRO]** The manufacturer shall securely handle various communication protocols beyond standard HTTP/HTTPS.

**Capability**: Support for custom schemes, WebSocket, WebRTC, and emerging web standards

**Conditions**:

- PRO-0: HTTP/HTTPS only
- PRO-1: Standard web protocols with strict validation
- PRO-2: Custom protocols with registration system
- PRO-3: Unrestricted protocol handler registration

**Threats**:

- Protocol confusion attacks
- Scheme hijacking
- Bypass of security controls via custom protocols
- Data leakage through protocol handlers
- Local application exploitation via URL schemes

**Risk**: MEDIUM - Custom protocols can bypass standard web security controls

**Requirements**:

#### PRO-0 Requirements (HTTP/HTTPS only)

- **PRO-0-REQ-1**: Browser shall only support HTTP and HTTPS protocols
- **PRO-0-REQ-2**: Browser shall reject all custom protocol handler registration attempts
- **PRO-0-REQ-3**: Browser shall block access to non-standard URL schemes (file://, data://, javascript://, etc.)
- **PRO-0-REQ-4**: Browser shall not provide registerProtocolHandler() API or equivalent functionality
- **PRO-0-REQ-5**: Browser shall reject navigation to any non-HTTP/HTTPS protocols

#### PRO-1 Requirements (Standard web protocols with strict validation)

- **PRO-1-REQ-1**: Browser shall validate all custom protocol handler registrations → Assessment: PRO-REQ-1
- **PRO-1-REQ-2**: Browser shall obtain explicit user consent before activating custom protocol handlers → Assessment: PRO-REQ-2
- **PRO-1-REQ-3**: Browser shall enforce protocol allowlists that restrict which custom schemes can be registered → Assessment: PRO-REQ-3
- **PRO-1-REQ-4**: Browser shall prevent scheme hijacking attacks → Assessment: PRO-REQ-4
- **PRO-1-REQ-5**: Browser shall sanitize protocol URL parameters before passing to handlers → Assessment: PRO-REQ-5
- **PRO-1-REQ-6**: Browser shall implement security controls for external protocol handlers → Assessment: PRO-REQ-6
- **PRO-1-REQ-7**: Browser shall provide transparent UI indicating protocol handler registration and invocation → Assessment: PRO-REQ-7
- **PRO-1-REQ-8**: Browser shall prevent protocol downgrade attacks → Assessment: PRO-REQ-8
- **PRO-1-REQ-9**: Browser shall log protocol handler registration, modification, and invocation events → Assessment: PRO-REQ-9
- **PRO-1-REQ-10**: Browser shall support web+custom scheme conventions → Assessment: PRO-REQ-10
- **PRO-1-REQ-11**: Browser shall enforce handler capability restrictions → Assessment: PRO-REQ-13
- **PRO-1-REQ-12**: Browser shall provide protocol handler revocation mechanisms → Assessment: PRO-REQ-14
- **PRO-1-REQ-13**: Browser shall enforce cross-origin protocol restrictions → Assessment: PRO-REQ-15

#### PRO-2 Requirements (Custom protocols with registration system)

- **PRO-2-REQ-1**: Browser shall implement all PRO-1 requirements
- **PRO-2-REQ-2**: Browser shall validate protocol handler persistence across sessions → Assessment: PRO-REQ-11
- **PRO-2-REQ-3**: Browser shall mitigate protocol confusion attacks → Assessment: PRO-REQ-12
- **PRO-2-REQ-4**: Browser shall validate protocol handler manifests → Assessment: PRO-REQ-16
- **PRO-2-REQ-5**: Browser shall integrate protocol handlers with Content Security Policy → Assessment: PRO-REQ-20
- **PRO-2-REQ-6**: Browser shall maintain audit trail for handler registrations → Assessment: PRO-REQ-21
- **PRO-2-REQ-7**: Browser shall enforce secure handler update mechanisms → Assessment: PRO-REQ-22
- **PRO-2-REQ-8**: Browser shall enforce handler isolation between origins → Assessment: PRO-REQ-23
- **PRO-2-REQ-9**: Browser shall support Intent URL security on Android platforms → Assessment: PRO-REQ-17
- **PRO-2-REQ-10**: Browser shall support Universal Links security on iOS platforms → Assessment: PRO-REQ-18
- **PRO-2-REQ-11**: Browser shall validate mobile deep linking security → Assessment: PRO-REQ-19
- **PRO-2-REQ-12**: Enterprise administrators shall be able to configure protocol handler allowlists and blocklists

#### PRO-3 Requirements (Unrestricted protocol registration)

- **PRO-3-REQ-1**: Browser shall implement baseline protocol handler validation → Assessment: PRO-REQ-1
- **PRO-3-REQ-2**: Browser shall obtain user consent for protocol handler activation → Assessment: PRO-REQ-2
- **PRO-3-REQ-3**: Browser shall sanitize protocol parameters → Assessment: PRO-REQ-5
- **PRO-3-REQ-4**: Browser shall implement external handler security controls → Assessment: PRO-REQ-6
- **PRO-3-REQ-5**: Browser shall provide handler management UI → Assessment: PRO-REQ-7
- **PRO-3-REQ-6**: Browser shall log protocol handler security events → Assessment: PRO-REQ-9
- **PRO-3-REQ-7**: Browser shall allow registration of custom schemes without web+ prefix
- **PRO-3-REQ-8**: Browser shall display security warnings for non-standard protocol handlers
- **PRO-3-REQ-9**: Browser shall provide user-accessible handler revocation controls → Assessment: PRO-REQ-14
- **PRO-3-REQ-10**: Users shall be able to review all registered protocol handlers in browser settings
- **PRO-3-REQ-11**: Browser shall scan custom handlers for known security vulnerabilities
- **PRO-3-REQ-12**: All protocol handler security exceptions shall be logged and auditable

### 5.7 Core Component Security

#### 5.7.1 System Resource Access

**[SYS]** The manufacturer shall implement secure boundaries between web content and system resources through Hardware Abstraction Layers and API mediation.

**Capability**: HAL implementation, PWA support, accessibility features, and local storage mechanisms

**Conditions**:

- SYS-0: Fully sandboxed with no system access
- SYS-1: Limited system access with strict permissions
- SYS-2: Extended system access for PWAs
- SYS-3: Native-equivalent system access

**Threats**:

- Sandbox escape attacks
- Unauthorized file system access
- Hardware fingerprinting
- Resource exhaustion attacks
- Accessibility feature abuse for screen reading

**Risk**: CRITICAL - System access breaches can compromise the entire host environment

**Requirements**:

#### SYS-0 Requirements (Fully sandboxed, no system access)

- **SYS-0-REQ-1**: Browser shall enforce process-level sandboxing for all web content → Assessment: SYS-REQ-1
- **SYS-0-REQ-2**: Browser shall isolate renderer processes from each other and browser core → Assessment: SYS-REQ-2
- **SYS-0-REQ-3**: Browser shall isolate GPU rendering in separate sandboxed process → Assessment: SYS-REQ-3
- **SYS-0-REQ-4**: Browser shall isolate network operations in separate process or service → Assessment: SYS-REQ-4
- **SYS-0-REQ-5**: Browser shall block all filesystem access from web content → Assessment: SYS-REQ-5
- **SYS-0-REQ-6**: Browser shall block all device API access (no camera, microphone, location, etc.)
- **SYS-0-REQ-7**: Browser shall enforce strict hardware resource limits → Assessment: SYS-REQ-20
- **SYS-0-REQ-8**: Browser shall enforce memory isolation between processes → Assessment: SYS-REQ-21
- **SYS-0-REQ-9**: Browser shall implement sandbox escape prevention mechanisms → Assessment: SYS-REQ-26
- **SYS-0-REQ-10**: Browser shall implement Spectre/Meltdown mitigations → Assessment: SYS-REQ-27
- **SYS-0-REQ-11**: Browser shall implement side-channel attack mitigations → Assessment: SYS-REQ-28
- **SYS-0-REQ-12**: Browser shall not expose any native messaging interfaces
- **SYS-0-REQ-13**: Browser shall block all host OS integration features

#### SYS-1 Requirements (Limited system access with strict permissions)

- **SYS-1-REQ-1**: Browser shall enforce process-level sandboxing → Assessment: SYS-REQ-1
- **SYS-1-REQ-2**: Browser shall isolate renderer processes → Assessment: SYS-REQ-2
- **SYS-1-REQ-3**: Browser shall isolate GPU process → Assessment: SYS-REQ-3
- **SYS-1-REQ-4**: Browser shall isolate network service → Assessment: SYS-REQ-4
- **SYS-1-REQ-5**: Browser shall enforce strict filesystem access controls → Assessment: SYS-REQ-5
- **SYS-1-REQ-6**: Browser shall implement permission controls for device hardware APIs → Assessment: SYS-REQ-6
- **SYS-1-REQ-7**: Browser shall enforce geolocation permission requirements → Assessment: SYS-REQ-8
- **SYS-1-REQ-8**: Browser shall enforce camera/microphone access controls with visible indicators → Assessment: SYS-REQ-9
- **SYS-1-REQ-9**: Browser shall restrict clipboard access to require user interaction → Assessment: SYS-REQ-10
- **SYS-1-REQ-10**: Browser shall enforce notification permission management → Assessment: SYS-REQ-11
- **SYS-1-REQ-11**: Browser shall restrict Sensor API access with permissions → Assessment: SYS-REQ-18
- **SYS-1-REQ-12**: Browser shall restrict Battery Status API to prevent fingerprinting → Assessment: SYS-REQ-19
- **SYS-1-REQ-13**: Browser shall enforce hardware resource limits → Assessment: SYS-REQ-20
- **SYS-1-REQ-14**: Browser shall enforce memory isolation → Assessment: SYS-REQ-21
- **SYS-1-REQ-15**: Browser shall implement CPU resource quotas → Assessment: SYS-REQ-22
- **SYS-1-REQ-16**: Browser shall enforce network bandwidth limits → Assessment: SYS-REQ-23
- **SYS-1-REQ-17**: Browser shall enforce storage quota limits → Assessment: SYS-REQ-24
- **SYS-1-REQ-18**: Browser shall implement process priority management → Assessment: SYS-REQ-25
- **SYS-1-REQ-19**: Browser shall prevent sandbox escapes → Assessment: SYS-REQ-26
- **SYS-1-REQ-20**: Browser shall implement speculative execution mitigations → Assessment: SYS-REQ-27
- **SYS-1-REQ-21**: Browser shall implement side-channel mitigations → Assessment: SYS-REQ-28
- **SYS-1-REQ-22**: Browser shall implement accessibility API security controls → Assessment: SYS-REQ-30

#### SYS-2 Requirements (Extended system access for PWAs)

- **SYS-2-REQ-1**: Browser shall implement all SYS-1 requirements
- **SYS-2-REQ-2**: Browser shall enforce equivalent permission controls for PWAs → Assessment: SYS-REQ-7
- **SYS-2-REQ-3**: Browser shall implement USB device access security → Assessment: SYS-REQ-12
- **SYS-2-REQ-4**: Browser shall enforce Bluetooth permission controls → Assessment: SYS-REQ-13
- **SYS-2-REQ-5**: Browser shall implement File System Access API security → Assessment: SYS-REQ-14
- **SYS-2-REQ-6**: Browser shall enforce WebUSB security controls → Assessment: SYS-REQ-15
- **SYS-2-REQ-7**: Browser shall enforce WebBluetooth security → Assessment: SYS-REQ-16
- **SYS-2-REQ-8**: Browser shall implement WebNFC permission management → Assessment: SYS-REQ-17
- **SYS-2-REQ-9**: Browser shall implement hardware token security → Assessment: SYS-REQ-29
- **SYS-2-REQ-10**: Browser shall enforce restricted native messaging with security controls → Assessment: SYS-REQ-31
- **SYS-2-REQ-11**: PWA permissions shall not exceed web context permissions
- **SYS-2-REQ-12**: PWA installation shall not auto-grant extended permissions
- **SYS-2-REQ-13**: PWA uninstallation shall revoke all granted permissions
- **SYS-2-REQ-14**: Browser shall maintain audit log of all PWA permission grants and revocations
- **SYS-2-REQ-15**: Enterprise administrators shall be able to configure PWA permission policies

#### SYS-3 Requirements (Native-equivalent system access)

- **SYS-3-REQ-1**: Browser shall implement baseline sandboxing for renderer processes → Assessment: SYS-REQ-1
- **SYS-3-REQ-2**: Browser shall enforce process isolation → Assessment: SYS-REQ-2
- **SYS-3-REQ-3**: Browser shall implement baseline permission controls for device APIs → Assessment: SYS-REQ-6
- **SYS-3-REQ-4**: Browser shall enforce filesystem access controls → Assessment: SYS-REQ-5
- **SYS-3-REQ-5**: Browser shall implement resource limits to prevent exhaustion → Assessment: SYS-REQ-20
- **SYS-3-REQ-6**: Browser shall implement memory isolation → Assessment: SYS-REQ-21
- **SYS-3-REQ-7**: Browser shall implement CPU quotas → Assessment: SYS-REQ-22
- **SYS-3-REQ-8**: Browser shall enforce storage quotas → Assessment: SYS-REQ-24
- **SYS-3-REQ-9**: Browser shall implement speculative execution mitigations → Assessment: SYS-REQ-27
- **SYS-3-REQ-10**: Browser shall implement side-channel mitigations → Assessment: SYS-REQ-28
- **SYS-3-REQ-11**: Browser shall enforce host OS integration security → Assessment: SYS-REQ-32
- **SYS-3-REQ-12**: Browser shall allow native-equivalent API access with user consent
- **SYS-3-REQ-13**: Browser shall provide transparent UI for all native integration features
- **SYS-3-REQ-14**: Browser shall display security warnings for privileged API access
- **SYS-3-REQ-15**: Browser shall log all extended system access for security auditing
- **SYS-3-REQ-16**: Users shall be able to review and revoke all system permissions
- **SYS-3-REQ-17**: Enterprise administrators shall be able to restrict native-equivalent features
- **SYS-3-REQ-18**: All native integration exceptions shall be documented and auditable

## 5.8 Embedded Browser Security

### 5.8.1 Overview

Embedded browsers (WebView components, browser engines integrated into native applications) present unique security challenges distinct from standalone browsers. While standalone browsers operate as independent applications with their own security boundaries, embedded browsers exist within a host application context where they navigate the security boundary between web content and the host application.

**Key Security Challenges**:

1. **Host-Code Injection**: Malicious web content may attempt to inject code into or manipulate the host application through JavaScript bridge interfaces, custom URL scheme handlers, or exploitation of WebView API vulnerabilities.

2. **User Data Exfiltration**: Web content loaded in an embedded browser may access sensitive data from the host application through insecure bridge configurations, shared storage, or insufficient isolation between web and native contexts.

3. **Insufficient Isolation**: Unlike standalone browsers where all web content is untrusted, embedded browsers often  establish trust relationships with certain content sources while maintaining security boundaries, creating complex policy enforcement challenges.

**Risk Classification**: CRITICAL - Vulnerabilities in embedded browser security can lead to complete compromise of the host application and exfiltration of all user data accessible to the host.

**Applicable Use Cases**: UC-B08 (Embedded Browser Component), UC-B09 (WebView Component in Native Applications), and aspects of UC-B10 (Adapted Browser with Modified Features) when the adaptation includes native component integration.

**References**:

- OWASP Mobile Security Testing Guide - WebViews: https://mas.owasp.org/MASTG/tests/android/MASVS-PLATFORM/MASTG-TEST-0028/
- Android WebView Security Best Practices: https://developer.android.com/develop/ui/views/layout/webapps/webview
- iOS WKWebView Security: https://developer.apple.com/documentation/webkit/wkwebview
- Chromium Embedded Framework Security: https://bitbucket.org/chromiumembedded/cef/wiki/GeneralUsage#markdown-header-security
- Electron Security Best Practices: https://www.electronjs.org/docs/latest/tutorial/security

### 5.8.2 Host Application Boundary Security

**[EMB]** The manufacturer shall implement secure isolation boundaries between embedded browser content and host application code, data, and resources.

**Capability**: JavaScript bridge security, native API exposure control, host data protection, and context isolation

**Conditions**:

- **EMB-0**: No JavaScript bridge or native API exposure (isolated WebView)
- **EMB-1**: Limited JavaScript bridge with explicit allowlist of safe APIs
- **EMB-2**: Extended JavaScript bridge with bidirectional communication
- **EMB-3**: Full integration with access to native capabilities and host data

**Threats**:

- JavaScript injection into host application context
- Unauthorized access to native APIs through bridge exploitation
- Code execution in host process via WebView vulnerabilities
- Cross-context data leakage between web and native layers
- Exploitation of insecure JavaScript bridge configurations
- Bypass of content security policies via native bridges
- Host application credential theft via bridge access
- Native code injection via crafted web content

**Risk**: CRITICAL - Compromise of the host-browser boundary can lead to complete application takeover and data exfiltration

**Requirements**:

#### EMB-0 Requirements (No JavaScript bridge or native API exposure)

- **EMB-0-REQ-1**: Embedded browser shall implement complete context isolation → Assessment: EMB-REQ-4
- **EMB-0-REQ-2**: Embedded browser shall isolate all storage from host application → Assessment: EMB-REQ-12
- **EMB-0-REQ-3**: Embedded browser shall enforce CSP for all web content → Assessment: EMB-REQ-13
- **EMB-0-REQ-4**: Embedded browser shall prevent all web content access to host application objects
- **EMB-0-REQ-5**: No JavaScript bridge or native API exposure mechanism shall exist
- **EMB-0-REQ-6**: Embedded browser shall treat all loaded content as completely untrusted
- **EMB-0-REQ-7**: Host application credentials shall be completely isolated from web context → Assessment: EMB-REQ-8

#### EMB-1 Requirements (Limited JavaScript bridge with explicit allowlist)

- **EMB-1-REQ-1**: JavaScript bridge shall implement explicit API allowlists with per-API access controls → Assessment: EMB-REQ-1
- **EMB-1-REQ-2**: All bridge data shall be validated, sanitized, and type-checked on native side → Assessment: EMB-REQ-2
- **EMB-1-REQ-3**: JavaScript bridge communications shall be logged → Assessment: EMB-REQ-3
- **EMB-1-REQ-4**: Embedded browser shall implement context isolation → Assessment: EMB-REQ-4
- **EMB-1-REQ-5**: Sensitive native APIs shall require explicit user consent → Assessment: EMB-REQ-5
- **EMB-1-REQ-6**: System-level APIs shall not be exposed without additional security controls → Assessment: EMB-REQ-6
- **EMB-1-REQ-7**: JavaScript bridge configuration shall be immutable after initialization → Assessment: EMB-REQ-7
- **EMB-1-REQ-8**: Web content shall not access host credentials, tokens, or keys → Assessment: EMB-REQ-8
- **EMB-1-REQ-9**: Bridge implementations shall be reviewed for injection vulnerabilities → Assessment: EMB-REQ-9
- **EMB-1-REQ-10**: Host shall implement rate limiting on bridge API calls → Assessment: EMB-REQ-10
- **EMB-1-REQ-11**: Bridge shall support granular capability-based permissions → Assessment: EMB-REQ-11
- **EMB-1-REQ-12**: Embedded browser shall isolate storage from host → Assessment: EMB-REQ-12
- **EMB-1-REQ-13**: Host shall enforce CSP for all embedded content → Assessment: EMB-REQ-13
- **EMB-1-REQ-14**: Web content shall not trigger misleading native UI → Assessment: EMB-REQ-15
- **EMB-1-REQ-15**: Host shall implement allowlists rather than denylists for bridge APIs → Assessment: EMB-REQ-16
- **EMB-1-REQ-16**: Only explicitly allowlisted APIs shall be accessible from web content
- **EMB-1-REQ-17**: Bridge API allowlist shall be minimal and documented

#### EMB-2 Requirements (Extended JavaScript bridge with bidirectional communication)

- **EMB-2-REQ-1**: All EMB-1 requirements shall be implemented
- **EMB-2-REQ-2**: Bridge communications crossing process boundaries shall be encrypted → Assessment: EMB-REQ-14
- **EMB-2-REQ-3**: Bridge shall implement granular permissions → Assessment: EMB-REQ-11
- **EMB-2-REQ-4**: Host shall implement comprehensive rate limiting → Assessment: EMB-REQ-10
- **EMB-2-REQ-5**: All bridge communications shall be logged with full audit trails → Assessment: EMB-REQ-3
- **EMB-2-REQ-6**: Bidirectional bridge calls shall maintain same security controls in both directions
- **EMB-2-REQ-7**: Web content callback handlers shall be validated before invocation
- **EMB-2-REQ-8**: Bridge shall implement message queuing with integrity protection
- **EMB-2-REQ-9**: Host shall monitor bridge traffic for anomalies
- **EMB-2-REQ-10**: Enterprise administrators shall be able to configure bridge API policies

#### EMB-3 Requirements (Full integration with native capabilities)

- **EMB-3-REQ-1**: Baseline EMB-1 security controls shall be maintained
- **EMB-3-REQ-2**: Bridge shall implement comprehensive input validation → Assessment: EMB-REQ-2
- **EMB-3-REQ-3**: Bridge shall log all operations with security context → Assessment: EMB-REQ-3
- **EMB-3-REQ-4**: Sensitive native operations shall require user consent → Assessment: EMB-REQ-5
- **EMB-3-REQ-5**: System-level APIs shall have strict additional controls → Assessment: EMB-REQ-6
- **EMB-3-REQ-6**: Bridge implementations shall undergo security review → Assessment: EMB-REQ-9
- **EMB-3-REQ-7**: Rate limiting shall prevent bridge API abuse → Assessment: EMB-REQ-10
- **EMB-3-REQ-8**: Full integration shall not bypass core security boundaries
- **EMB-3-REQ-9**: User shall be informed of all native capabilities granted to web content
- **EMB-3-REQ-10**: User shall be able to review and revoke native API access
- **EMB-3-REQ-11**: All native integrations shall be documented and auditable
- **EMB-3-REQ-12**: Enterprise policies shall be able to restrict native integration scope

### 5.8.3 Content Source Trust Management

**[EMB]** The manufacturer shall implement mechanisms to establish and enforce trust relationships between embedded browser content sources and the host application.

**Capability**: Content source validation, certificate pinning for embedded content, subresource integrity, and trust boundary enforcement

**Conditions**:

- **EMB-0**: All content treated as untrusted (public internet)
- **EMB-1**: Trusted domains with certificate validation
- **EMB-2**: Certificate pinning for specific trusted origins
- **EMB-3**: Local/bundled content with cryptographic verification

**Threats**:

- Man-in-the-middle attacks against trusted content sources
- Loading of malicious content from compromised trusted domains
- Bypass of trust boundaries through redirect chains
- Subresource substitution attacks
- DNS hijacking of embedded content sources
- Certificate authority compromise affecting trusted origins
- Mixed content attacks (trusted page loading untrusted resources)
- Cache poisoning affecting embedded content

**Risk**: CRITICAL - Compromise of trusted content sources can lead to injection of malicious code with elevated privileges

**Requirements**:

#### EMB-0 Requirements (All content treated as untrusted - public internet)

- **EMB-0-REQ-1**: All content shall be treated as completely untrusted
- **EMB-0-REQ-2**: Embedded browser shall validate SSL/TLS certificates for all remote content → Assessment: EMB-REQ-17
- **EMB-0-REQ-3**: Embedded browser shall prevent all mixed content → Assessment: EMB-REQ-21
- **EMB-0-REQ-4**: Certificate validation failures shall block content loading → Assessment: EMB-REQ-26
- **EMB-0-REQ-5**: Network security configuration shall prevent cleartext traffic → Assessment: EMB-REQ-27
- **EMB-0-REQ-6**: Trust boundary violations shall trigger security events → Assessment: EMB-REQ-32
- **EMB-0-REQ-7**: No content origin shall have privileged access
- **EMB-0-REQ-8**: All CSP policies shall be strictly enforced without exceptions

#### EMB-1 Requirements (Trusted domains with certificate validation)

- **EMB-1-REQ-1**: Embedded browser shall validate SSL/TLS certificates for all remote content → Assessment: EMB-REQ-17
- **EMB-1-REQ-2**: Host shall implement allowlist of trusted content origins → Assessment: EMB-REQ-18
- **EMB-1-REQ-3**: Embedded browser shall prevent mixed content → Assessment: EMB-REQ-21
- **EMB-1-REQ-4**: Trust decisions shall be logged with full context → Assessment: EMB-REQ-22
- **EMB-1-REQ-5**: Host shall implement redirect chain validation → Assessment: EMB-REQ-24
- **EMB-1-REQ-6**: Embedded browser shall enforce HSTS for trusted origins → Assessment: EMB-REQ-25
- **EMB-1-REQ-7**: Certificate failures shall trigger immediate notification and blocking → Assessment: EMB-REQ-26
- **EMB-1-REQ-8**: Network security config shall prevent cleartext to trusted domains → Assessment: EMB-REQ-27
- **EMB-1-REQ-9**: Trusted content shall not load untrusted third-party content without CSP → Assessment: EMB-REQ-28
- **EMB-1-REQ-10**: Trust boundary violations shall trigger security events → Assessment: EMB-REQ-32
- **EMB-1-REQ-11**: Only explicitly allowlisted origins shall be considered trusted
- **EMB-1-REQ-12**: Trust allowlist shall be immutable by web content

#### EMB-2 Requirements (Certificate pinning for specific trusted origins)

- **EMB-2-REQ-1**: All EMB-1 requirements shall be implemented
- **EMB-2-REQ-2**: Embedded browser shall implement certificate pinning for critical origins → Assessment: EMB-REQ-17
- **EMB-2-REQ-3**: Embedded browser shall enforce SRI for external scripts from trusted content → Assessment: EMB-REQ-19
- **EMB-2-REQ-4**: Certificate pinning shall include backup pins and rotation mechanisms → Assessment: EMB-REQ-20
- **EMB-2-REQ-5**: Trust policies shall be configurable per browser instance → Assessment: EMB-REQ-29
- **EMB-2-REQ-6**: Embedded browser shall implement certificate transparency verification → Assessment: EMB-REQ-30
- **EMB-2-REQ-7**: Host shall detect and prevent DNS rebinding attacks → Assessment: EMB-REQ-31
- **EMB-2-REQ-8**: Pin configuration shall be immutable after initialization
- **EMB-2-REQ-9**: Pinning violations shall immediately block content loading
- **EMB-2-REQ-10**: Pin rotation procedures shall be documented and tested

#### EMB-3 Requirements (Local/bundled content with cryptographic verification)

- **EMB-3-REQ-1**: Baseline EMB-1 certificate validation shall apply to all remote content
- **EMB-3-REQ-2**: Embedded browser shall verify cryptographic signatures for local/bundled content → Assessment: EMB-REQ-23
- **EMB-3-REQ-3**: Embedded browser shall enforce SRI for all external scripts → Assessment: EMB-REQ-19
- **EMB-3-REQ-4**: Certificate pinning shall be enforced for remote trusted origins → Assessment: EMB-REQ-17, EMB-REQ-20
- **EMB-3-REQ-5**: Trust decisions shall be logged comprehensively → Assessment: EMB-REQ-22
- **EMB-3-REQ-6**: Trust policies shall be configurable per instance → Assessment: EMB-REQ-29