XSLT document loading did not correctly propagate the source document which bypassed its CSP. This vulnerability affects Firefox < 141, Firefox ESR < 128.13, Firefox ESR < 140.1, Thunderbird < 141, Thunderbird < 128.13, and Thunderbird < 140.1.
https://www.mozilla.org/security/advisories/mfsa2025-63/
https://www.mozilla.org/security/advisories/mfsa2025-62/
https://www.mozilla.org/security/advisories/mfsa2025-61/
https://www.mozilla.org/security/advisories/mfsa2025-59/
https://www.mozilla.org/security/advisories/mfsa2025-58/