CVE-2025-3859: Mozilla Firefox Focus

Medium severity, CVSS 6.1. EPSS: 0.2% chance of exploitation in the next 30 days.

Websites directing users to long URLs that caused eliding to occur in the location view could leverage the truncating behavior to potentially trick users into thinking they were on a different webpage. This vulnerability was fixed in Focus 138.

Affected products

• Mozilla Firefox Focus: before 138.0 (fixed in 138.0)

Published 2025-04-30. Last modified 2026-06-17.