Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
https://www.mozilla.org/security/advisories/mfsa2026-17/
https://www.mozilla.org/security/advisories/mfsa2026-16/
https://www.mozilla.org/security/advisories/mfsa2026-15/
https://www.mozilla.org/security/advisories/mfsa2026-14/