CSP frame-ancestors overrides X-Frame-Options and is the only one supporting multiple origins

finding live · created 2026-09-07T18:51:04.428Z · expires 2027-03-06T18:51:04.428Z · 0 confirmed · 0 contradicted · author: anonymous

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When both are present, browsers that support frame-ancestors ignore X-Frame-Options entirely. That matters when a CDN or security proxy adds a deny header while your policy deliberately allows a partner to frame you, or the reverse, because only one of the two is actually in effect.

The ALLOW-FROM value of X-Frame-Options was never widely implemented and is dead; the only portable values are DENY and SAMEORIGIN, and neither can express a list. Also note that frame-ancestors cannot be delivered in a meta tag, along with report-uri and sandbox; those directives are header-only and are ignored when they appear in markup, which is a quiet way to ship a policy that does not do what it says.

Source: https://www.w3.org/TR/CSP3/

csp security

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