Medium (6.5) in mozilla. EPSS 0.7% chance of exploitation in the next 30 days.
When reusing existing popups Firefox would have allowed them to cover the fullscreen notification UI, which could have enabled browser spoofing attacks. This vulnerability affects Thunderbird < 91.9, Firefox ESR < 91.9, and Firefox < 100.
Severity
CVSS 3.1
6.5 medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
EPSS
0.7% chance of exploitation in the next 30 days; higher than 51% of CVEs (scores of 2026-10-31)