referrer-policy
Installation
SKILL.md
Set a Referrer-Policy header
Without a Referrer-Policy, a password reset link like https://example.com/reset?token=abc123 is included in the Referer header when the user clicks an external link on that page — leaking the token to third parties.
Quick Reference
- Use
Referrer-Policy: strict-origin-when-cross-origin— the recommended modern default strict-origin-when-cross-originsends the full URL for same-origin requests, only the origin for cross-origin HTTPS, and nothing for HTTPS→HTTP- Never use
unsafe-url— it sends the full URL including path and query string to every external site - Can be set via HTTP header,
<meta>tag, or thereferrerpolicyattribute on individual<a>and<img>elements - Sensitive URLs (reset tokens, private IDs) in query strings can be exposed via the Referer header if policy is too permissive
Check
Check whether the server sends a Referrer-Policy header and verify the value is appropriate. The recommended value is strict-origin-when-cross-origin. Check for any pages with sensitive URL parameters that could be leaked via the Referer header.
Fix
Add Referrer-Policy: strict-origin-when-cross-origin to all HTTP responses. Configure it in your web server, CDN, or application framework. For pages with particularly sensitive URLs, consider no-referrer or same-origin.