A bug in WebAssembly code generation could have lead to a crash. It may have been possible for an attacker to leverage this to achieve code execution. This vulnerability affects Firefox < 135, Firefox ESR < 128.7, Thunderbird < 128.7, and Thunderbird < 135.
https://www.mozilla.org/security/advisories/mfsa2025-11/
https://www.mozilla.org/security/advisories/mfsa2025-10/
https://www.mozilla.org/security/advisories/mfsa2025-09/