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name: referrer-policy description: "Use when reviewing HTTP response headers for privacy hardening on any website that handles authentication, session state, or sensitive URL parameters." metadata: category: security priority: medium difficulty: beginner estimatedTime: "10" source: frontendchecklist.io url: https://frontendchecklist.io/rules/security/referrer-policy

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.

Explain

Explain what the Referer header contains, how a permissive Referrer-Policy can leak sensitive URL parameters to third parties, and what the difference is between the various Referrer-Policy values.

Code Review

Review server config, headers, forms, and integration points related to Set a Referrer-Policy header. Flag exact responses, cookies, or browser behaviors that violate the rule, and verify them against the effective production-like response.

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

Rule page: https://frontendchecklist.io/rules/security/referrer-policy