frontend-security-coder

Use textContent instead of innerHTML for plain text, and sanitize HTML with DOMPurify before insertion when rich formatting is required. Combine this with a strict Content Security Policy to block injected scripts as a defense-in-depth measure.

Start with report-only mode to collect violations, then enforce directives like script-src with nonces or hashes instead of unsafe-inline. Move inline scripts to external files and progressively tighten directives while monitoring violation reports.

localStorage tokens are accessible to any JavaScript on the page, making them vulnerable to XSS theft. HttpOnly cookies with SameSite attributes offer better protection, though they require CSRF defenses; the choice depends on your threat model.

Frame-busting and X-Frame-Options can break legitimate iframe embedding during development. Apply clickjacking protection only in production or standalone deployments, and relax it in development environments that require iframe embedding.

Use secure coding guidance for hands-on implementation like XSS fixes and CSP setup. Use a security auditor for high-level assessments such as compliance reviews, threat modeling, penetration testing planning, and security architecture evaluation.