CVE-2021-23969

As specified in the W3C Content Security Policy draft, when creating a violation report, "User agents need to ensure that the source file is the URL requested by the page, pre-redirects. If that’s not possible, user agents need to strip the URL down to an origin to avoid unintentional leakage." Under certain types of redirects, Firefox incorrectly set the source file to be the destination of the redirects. This was fixed to be the redirect destination's origin. This vulnerability affects Firefox < 86, Thunderbird < 78.8, and Firefox ESR < 78.8.

• https://bugzilla.mozilla.org/show_bug.cgi?id=1542194Issue Tracking, Permissions Required, Vendor Advisory
• https://lists.debian.org/debian-lts-announce/2021/03/msg00000.htmlMailing List, Third Party Advisory
• https://security.gentoo.org/glsa/202104-09Third Party Advisory
• https://security.gentoo.org/glsa/202104-10Third Party Advisory
• https://www.debian.org/security/2021/dsa-4866Third Party Advisory
• https://www.mozilla.org/security/advisories/mfsa2021-07/Release Notes, Vendor Advisory
• https://www.mozilla.org/security/advisories/mfsa2021-08/Release Notes, Vendor Advisory
• https://www.mozilla.org/security/advisories/mfsa2021-09/Release Notes, Vendor Advisory
• https://bugzilla.mozilla.org/show_bug.cgi?id=1542194Issue Tracking, Permissions Required, Vendor Advisory
• https://lists.debian.org/debian-lts-announce/2021/03/msg00000.htmlMailing List, Third Party Advisory
• https://security.gentoo.org/glsa/202104-09Third Party Advisory
• https://security.gentoo.org/glsa/202104-10Third Party Advisory
• https://www.debian.org/security/2021/dsa-4866Third Party Advisory
• https://www.mozilla.org/security/advisories/mfsa2021-07/Release Notes, Vendor Advisory
• https://www.mozilla.org/security/advisories/mfsa2021-08/Release Notes, Vendor Advisory
• https://www.mozilla.org/security/advisories/mfsa2021-09/Release Notes, Vendor Advisory

Published

Feb 26, 2021

Last Modified

Jun 17, 2026

Status

Modified

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