Medium (6.5). EPSS 1.4% chance of exploitation in the next 30 days.
When in an endless loop, a website specifying a custom cursor using CSS could make it look like the user is interacting with the user interface, when they are not. This could lead to a perceived broken state, especially when interactions with existing browser dialogs and warnings do not work. This vulnerability affects Firefox ESR < 78.1, Firefox < 79, and Thunderbird < 78.1.
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
1.4% chance of exploitation in the next 30 days; higher than 72% of CVEs (scores of 2026-10-31)