Under certain conditions, Firefox did not display a warning when a user attempted to navigate to a new protocol handler. This vulnerability affects Firefox < 121.
Severity
CVSS 3.1
4.3 medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
EPSS
0.5% chance of exploitation in the next 30 days; higher than 42% of CVEs (scores of 2026-10-31)