Set an X-Frame-Options header

Without framing protection, an attacker can embed your banking login page in a transparent iframe on a malicious site and trick users into clicking buttons they cannot see — transferring money, changing settings, or leaking credentials.

Quick Reference

• Use X-Frame-Options: DENY to prevent all framing, or SAMEORIGIN to allow framing only from your own domain
• ALLOWFROM is obsolete and unsupported in modern browsers — use CSP frame-ancestors instead
• The modern equivalent is Content-Security-Policy: frame-ancestors 'none' — prefer CSP for new sites
• Both headers can coexist: X-Frame-Options for older browsers, frame-ancestors for modern ones
• Clickjacking attacks trick users into clicking invisible iframe buttons — DENY eliminates this entirely

Check

Check whether the server sends an X-Frame-Options header (DENY or SAMEORIGIN) or a Content-Security-Policy header with frame-ancestors directive to prevent clickjacking.

Fix

Add X-Frame-Options: DENY to all responses if the site does not need to be embedded anywhere. If legitimate framing is needed on the same origin, use SAMEORIGIN. For fine-grained control, use CSP frame-ancestors instead.

Explain

Explain what a clickjacking attack is, how X-Frame-Options and CSP frame-ancestors prevent it, and the difference between DENY and SAMEORIGIN values.

Code Review

Review server config, headers, forms, and integration points related to Set an X-Frame-Options 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/en/rules/security/x-frame-options