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-origin sends 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 the referrerpolicy attribute 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.

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referrer-policy — thedaviddias/front-end-checklist