CVE-2025-1935: Mozilla Firefox

Medium severity, CVSS 4.3. EPSS: 0.3% chance of exploitation in the next 30 days.

A web page could trick a user into setting that site as the default handler for a custom URL protocol. This vulnerability was fixed in Firefox 136, Firefox ESR 128.8, Thunderbird 136, and Thunderbird 128.8.

Affected products

• Mozilla Firefox: before 128.8.0 (fixed in 128.8.0); before 136.0 (fixed in 136.0)
• Mozilla Thunderbird: before 128.8.0 (fixed in 128.8.0); from 129.0, before 136.0 (fixed in 136.0)

Published 2025-03-04. Last modified 2026-10-05.