Add Subresource Integrity to external scripts

When you load JavaScript from a CDN, you're trusting that CDN completely — if it's compromised, attackers can serve malicious JavaScript to all your users. SRI adds a cryptographic hash to the tag; the browser refuses to execute the script if the hash doesn't match the downloaded content, protecting users even if the CDN is compromised or the URL is hijacked.

Quick Reference

• Add integrity="sha384-..." to
• Always pair integrity with crossorigin="anonymous"
• Generate hashes with openssl or online tools — CDN providers usually supply them
• SRI blocks execution if the file hash doesn't match, preventing CDN compromise attacks

Check

Find all external

Fix

Add appropriate integrity and crossorigin attributes to external CDN resources. Generate the SHA-384 hashes for each resource.

Explain

Explain Subresource Integrity, how it protects against CDN compromise, how to generate SRI hashes, and its limitations.

Code Review

Review templates, server-rendered HTML, and shared components that output markup related to Add Subresource Integrity to external scripts. Flag exact elements, attributes, and routes where the rendered HTML violates the rule.

---

For full implementation details, code examples, and framework-specific guidance, see references/rule.md.

Rule page: https://frontendchecklist.io/en/rules/html/subresource-integrity