Same-origin policy bypass in the DevTools component. This vulnerability was fixed in Firefox 158 and Thunderbird 158.
https://www.mozilla.org/security/advisories/mfsa2026-109/
https://www.mozilla.org/security/advisories/mfsa2026-106/
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-98532
https://bugzilla.mozilla.org/show_bug.cgi?id=2066063
Source: Mitre, NVD
Published: 2026-10-13
Updated: 2026-10-13
Base Score: 6.4
Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:N
Severity: Medium
Base Score: 9.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Severity: Critical
EPSS: 0.00157