Stylesheets via CDN without Subresource Integrity
- December 7, 2025
- Security, Resource Integrity
Element Code: SE-009
Quick Reference
Issue: CDN-hosted CSS lacks integrity attributes
Impact: Vulnerable to CDN compromise affecting styles
Fix: Add integrity attribute with hash to CDN link tags
Detection: Security audits
What Is This Issue?
Like JavaScript, CSS from CDNs can be compromised. While less dangerous than script injection, malicious CSS can still hide content, create phishing overlays, or exfiltrate data.
Why This Matters for Your Website
CSS attacks are less common but possible. SRI on stylesheets provides defense in depth.
How to Fix This Issue
- Generate hash: SHA-384 or SHA-512
- Add integrity: To link rel="stylesheet" tags
- Add crossorigin: Required for SRI
Tools for Detection
- SRI Hash Generator: Generate integrity hashes
TL;DR (The Simple Version)
Your CDN stylesheets lack integrity checks. Add integrity attributes to verify CSS has not been tampered with.
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