Frontend Security Red Book: Latest XSS/CSRF Defense Strategies in 2024

May 22, 2025
:94  :0

Frontend Security Red Book: Latest XSS/CSRF Defense Strategies in 2024

In the ever-evolving landscape of web security, Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF) remain two of the most critical threats to frontend applications. As attackers refine their techniques, developers must adopt the latest defense mechanisms to safeguard user data and maintain application integrity.

This guide explores cutting-edge strategies to mitigate XSS and CSRF in 2024, with a focus on CSP nonce and Trusted Types for robust protection.

1. Strengthening XSS Defenses

(1) Content Security Policy (CSP) with Nonce

CSP is a powerful HTTP header that restricts the sources of executable scripts, effectively preventing inline script injection attacks.

Key Implementation:

  • Use a randomized nonce for each request to allow only trusted scripts.
  • Configure CSP in the HTTP header:
Content-Security-Policy: script-src 'nonce-{RANDOM}' 'strict-dynamic' https:; object-src 'none'; base-uri 'self';

How It Works:

  • The server generates a unique nonce for each response.
  • Only scripts with the correct nonce execute:
<script nonce="{RANDOM}">  
  // Trusted script runs  
</script>

(2) Trusted Types for DOM XSS Prevention

Trusted Types is a browser API that eliminates DOM-based XSS by enforcing secure coding practices.

Setup:

  1. Enable Trusted Types via CSP:

    Content-Security-Policy: require-trusted-types-for 'script';

  2. Define a Trusted Types policy:

    if (window.trustedTypes) {
  const policy = trustedTypes.createPolicy('default', {
    createHTML: (input) => DOMPurify.sanitize(input),
  });
}

Result:

  • All unsafe DOM assignments (e.g., innerHTML) are blocked unless sanitized.
  • Forces developers to use safe methods for dynamic content.

2. CSRF Protection in 2024

(1) SameSite Cookies (Strict/Lax)

Modern browsers enforce SameSite cookie attributes to block CSRF by default.

Best Practices:

  • Set SameSite=Lax for non-sensitive cookies (allows GET requests from same site).
  • Use SameSite=Strict for high-security cookies (blocks all cross-origin requests).
Set-Cookie: sessionId=abc123; SameSite=Strict; Secure; HttpOnly

(2) Anti-CSRF Tokens

Still a must-have for state-changing requests (POST, PUT, DELETE).

Implementation:

  • Generate a unique token per session:

    const csrfToken = crypto.randomUUID();

  • Embed it in forms or headers:

    <input type="hidden" name="_csrf" value="{{csrfToken}}">

  • Validate server-side on each request.

(3) Origin & Referrer Headers Check

Verify Origin or Referer headers to block cross-origin requests:

app.post('/transfer', (req, res) => {
  if (req.get('Origin') !== 'https://trusted-site.com') {
    return res.status(403).send('Invalid origin');
  }
  // Process request
});

3. Bonus: Secure Development Practices

  • Avoid eval() and innerHTML – Use textContent or Trusted Types.
  • Use Subresource Integrity (SRI) – Ensures third-party scripts are unaltered.
  • Regular Dependency Audits – Tools like npm audit or OWASP ZAP.

Conclusion

In 2024, CSP nonce and Trusted Types are game-changers for XSS defense, while SameSite cookies + CSRF tokens remain essential for CSRF protection. By adopting these strategies, developers can build resilient frontend applications against evolving threats.

Stay secure, and happy coding! 🚀

Further Reading: