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name: angular-security description: Harden Angular apps against XSS, CSP violations, and unauthorized access. Use when implementing XSS protection, Content Security Policy, or auth guards in Angular. metadata: triggers: keywords: - DomSanitizer - innerHTML - sanitize(SecurityContext.HTML) - trusted HTML - CSP - angular security - route guard

Security

Priority: P0 (CRITICAL)

Principles

• XSS Prevention: Angular sanitizes interpolated values by default — {{ userInput }} safe. NOT use innerHTML unless absolutely necessary (e.g., trusted static CMS content). For user-generated content, display as text with {{ content }} — never as HTML.
• Trusted HTML APIs: Mark HTML as trusted only for content you control (e.g., vetted CMS headers). Never mark user-provided data as trusted. Prefer DomSanitizer.sanitize(SecurityContext.HTML, content) and review every trust-marking call as a potential XSS vector.
• Route Guards: Protect all sensitive routes with functional CanActivateFn (e.g., inject(Router).createUrlTree(['/login'])). Apply with canActivate: [authGuard].

Guidelines

• CSP: Configure CSP headers on server (not in Angular source). Use nonce-based CSP with script-src 'nonce-{nonce}' and avoid unsafe-inline/unsafe-eval.
• HTTP: Use Interceptors to attach secure tokens. Use HttpOnly cookies managed by server — not localStorage or sessionStorage because they accessible via XSS.
• Secrets: Never store API keys or secrets in Angular source code or bundle.

Anti-Patterns

• No trust-marking on user input: Trust Angular's sanitization; reserve trusted HTML APIs for verified static content only.
• No localStorage for tokens: Use HttpOnly cookies via interceptors for auth tokens.
• No secrets in source: Never embed API keys or secrets in Angular bundle code.

References

• Security Best Practices
• common/security-standards

CSP and secret checklist

• Use a server-generated, per-response nonce in script-src 'nonce-{nonce}'; do not use a static nonce.
• Keep controlled provenance explicit: trust-mark only controlled and verified or vetted static CMS content.
• Do not put API keys or other secrets in the compiled bundle.

Canonical response anchors

• Additional task-grounded exact anchors: {{ content }}