# CVE-2021-23969: Firefox ESR and 2 others: As specified in the W3C Content Security Policy draft, when creating a violation report, "User agents… CVE-2021-23969 is fixed in 11 products on 2 platforms, first by RHSA-2021:0655, released February 24, 2021. It is not reported as exploited. Patch Radar priority: Urgent. - Web page: https://patchblox.com/security/cve/CVE-2021-23969 - Priority: Urgent - CVSS: 4.3 (Critical) - EPSS: 0.0121 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Feb 24, 2021 - Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2021-23969 ## Description 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. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Windows apps | Mozilla Firefox ESR (en-US) | 91.0 | [Mozilla Firefox ESR (en-US) 91.0](https://patchblox.com/security/data/fix/windows-app/mozilla.firefox.esr-91.0.md) | Aug 4, 2021 | | Windows apps | Mozilla Thunderbird (en-US) | 78.10.0 | [Mozilla Thunderbird (en-US) 78.10.0](https://patchblox.com/security/data/fix/windows-app/mozilla.thunderbird-78.10.0.md) | Apr 15, 2021 | | Linux | firefox RHEL 8 | 0:78.8.0-1.el8_3 | [RHSA-2021:0655](https://patchblox.com/security/data/fix/linux/rhsa-2021-0655.md) | Feb 24, 2021 | | Linux | firefox Ubuntu 18.04.6 LTS (bionic) | 86.0+build3-0ubuntu0.18.04.1 | [firefox 86.0+build3-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-86.0-build3-0ubuntu0.18.04.1.md) | Feb 26, 2021 | | Linux | firefox Ubuntu 20.04 LTS (focal) | 86.0+build3-0ubuntu0.20.04.1 | [firefox 86.0+build3-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-86.0-build3-0ubuntu0.20.04.1.md) | Feb 26, 2021 | | Linux | firefox ol 8 | 0:78.8.0-1.0.1.el8_3 | [ELSA-2021-0655](https://patchblox.com/security/data/fix/linux/elsa-2021-0655.md) | Feb 26, 2021 | | Linux | firefox-geckodriver Ubuntu 18.04.6 LTS (bionic) | 86.0+build3-0ubuntu0.18.04.1 | [firefox-geckodriver 86.0+build3-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-geckodriver-86.0-build3-0ubuntu0.18.04.1.md) | Feb 26, 2021 | | Linux | firefox-geckodriver Ubuntu 20.04 LTS (focal) | 86.0+build3-0ubuntu0.20.04.1 | [firefox-geckodriver 86.0+build3-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-geckodriver-86.0-build3-0ubuntu0.20.04.1.md) | Feb 26, 2021 | | Linux | firefox-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 86.0+build3-0ubuntu0.18.04.1 | [firefox-mozsymbols 86.0+build3-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-mozsymbols-86.0-build3-0ubuntu0.18.04.1.md) | Feb 26, 2021 | | Linux | firefox-mozsymbols Ubuntu 20.04 LTS (focal) | 86.0+build3-0ubuntu0.20.04.1 | [firefox-mozsymbols 86.0+build3-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-firefox-mozsymbols-86.0-build3-0ubuntu0.20.04.1.md) | Feb 26, 2021 | | Linux | thunderbird RHEL 8 | 0:78.8.0-1.el8_3 | [RHSA-2021:0657](https://patchblox.com/security/data/fix/linux/rhsa-2021-0657.md) | Feb 24, 2021 | | Linux | thunderbird Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | [thunderbird 1:78.8.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-thunderbird-1-78.8.1-build1-0ubuntu0.18.04.1.md) | Apr 22, 2021 | | Linux | thunderbird Ubuntu 20.04 LTS (focal) | 1:78.8.1+build1-0ubuntu0.20.04.1 | [thunderbird 1:78.8.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-thunderbird-1-78.8.1-build1-0ubuntu0.20.04.1.md) | Apr 22, 2021 | | Linux | thunderbird ol 8 | 0:78.8.0-1.0.1.el8_3 | [ELSA-2021-0657](https://patchblox.com/security/data/fix/linux/elsa-2021-0657.md) | Feb 26, 2021 | | Linux | thunderbird-gnome-support Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | [thunderbird-gnome-support 1:78.8.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-thunderbird-gnome-support-1-78.8.1-build1-0ubuntu0.18.04.1.md) | Apr 22, 2021 | | Linux | thunderbird-gnome-support Ubuntu 20.04 LTS (focal) | 1:78.8.1+build1-0ubuntu0.20.04.1 | [thunderbird-gnome-support 1:78.8.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-thunderbird-gnome-support-1-78.8.1-build1-0ubuntu0.20.04.1.md) | Apr 22, 2021 | | Linux | thunderbird-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | [thunderbird-mozsymbols 1:78.8.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-thunderbird-mozsymbols-1-78.8.1-build1-0ubuntu0.18.04.1.md) | Apr 22, 2021 | | Linux | thunderbird-mozsymbols Ubuntu 20.04 LTS (focal) | 1:78.8.1+build1-0ubuntu0.20.04.1 | [thunderbird-mozsymbols 1:78.8.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-thunderbird-mozsymbols-1-78.8.1-build1-0ubuntu0.20.04.1.md) | Apr 22, 2021 | | Linux | xul-ext-calendar-timezones Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | [xul-ext-calendar-timezones 1:78.8.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-xul-ext-calendar-timezones-1-78.8.1-build1-0ubuntu0.18.04.1.md) | Apr 22, 2021 | | Linux | xul-ext-calendar-timezones Ubuntu 20.04 LTS (focal) | 1:78.8.1+build1-0ubuntu0.20.04.1 | [xul-ext-calendar-timezones 1:78.8.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-xul-ext-calendar-timezones-1-78.8.1-build1-0ubuntu0.20.04.1.md) | Apr 22, 2021 | | Linux | xul-ext-gdata-provider Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | [xul-ext-gdata-provider 1:78.8.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-xul-ext-gdata-provider-1-78.8.1-build1-0ubuntu0.18.04.1.md) | Apr 22, 2021 | | Linux | xul-ext-gdata-provider Ubuntu 20.04 LTS (focal) | 1:78.8.1+build1-0ubuntu0.20.04.1 | [xul-ext-gdata-provider 1:78.8.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-xul-ext-gdata-provider-1-78.8.1-build1-0ubuntu0.20.04.1.md) | Apr 22, 2021 | | Linux | xul-ext-lightning Ubuntu 18.04.6 LTS (bionic) | 1:78.8.1+build1-0ubuntu0.18.04.1 | [xul-ext-lightning 1:78.8.1+build1-0ubuntu0.18.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-xul-ext-lightning-1-78.8.1-build1-0ubuntu0.18.04.1.md) | Apr 22, 2021 | | Linux | xul-ext-lightning Ubuntu 20.04 LTS (focal) | 1:78.8.1+build1-0ubuntu0.20.04.1 | [xul-ext-lightning 1:78.8.1+build1-0ubuntu0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-xul-ext-lightning-1-78.8.1-build1-0ubuntu0.20.04.1.md) | Apr 22, 2021 | --- Data as of 2026-11-08T00:53:09Z UTC. 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