TypeScript Security

Priority: P0 (CRITICAL)

Validate Input at Boundaries

• Use Zod, Joi, or class-validator at API boundary. Always parse and validate user-controlled input before using. Use safeParse for error handling without throwing. Return 400 with structured errors on failure.

See references/REFERENCE.md for Zod validation schemas, secure cookie setup, and JWT auth patterns.

Prevent Injection and XSS

• Sanitization: Use DOMPurify for HTML sanitization to prevent Cross-Site Scripting (XSS).
• SQL Injection: Use Parameterized Queries (e.g., pool.query('... WHERE id = $1', [id])) or Type-safe ORMs (Prisma/TypeORM). Use Prisma.sql for raw queries.
• Input Filtering: Sanitize user-controlled input before using it in file paths or OS commands (Command Injection).

Secure Authentication

• Use Argon2id for password hashing. Implement JWT (via jsonwebtoken or jose) with HttpOnly and Secure cookies. Use RS256 for public/private key pairs and implement Refresh Token rotation.
• Secrets: Store secrets in .env (e.g., JWT_SECRET) or Secret Managers. NEVER commit them to Git.
• CORS: Configure CORS with Strict Origin Whitelisting. Avoid origin: '*'.
• Encryption: Use crypto (Node.js) or Web Crypto API for sensitive data. Avoid legacy algorithms like MD5/SHA1.

Verification

After typing validation schemas (Zod/joi) or auth guards, call getDiagnostics (typescript-lsp) to confirm type narrowing correct before finalizing.

Anti-Patterns