CVE-2023-6871: Mozilla Firefox

Medium severity, CVSS 4.3. EPSS: 0.5% chance of exploitation in the next 30 days.

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.

Affected products

• Mozilla Firefox: before 121.0 (fixed in 121.0)

Published 2023-12-19. Last modified 2026-06-17.