Privilege escalation in the Application Update component. This vulnerability was fixed in Firefox 154 and Thunderbird 154.
https://www.mozilla.org/security/advisories/mfsa2026-78/
https://www.mozilla.org/security/advisories/mfsa2026-74/
https://bugzilla.mozilla.org/show_bug.cgi?id=2021757
Source: Mitre, NVD
Published: 2026-08-18
Updated: 2026-08-18
Base Score: 10
Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:C
Severity: Critical
Base Score: 8.8
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Severity: High