CVE-2025-1935: Clickjacking the registerProtocolHandler info-bar

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-03-04 · updated 2026-10-05
Weakness: CWE-79

Description

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; before 136.0 — fixed in 128.8.0, 136.0
Mozilla Thunderbird: before 128.8.0; from 129.0 before 136.0 — fixed in 128.8.0, 136.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 128.8.0, 136.0; Mozilla Thunderbird 128.8.0, 136.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1866661
https://www.mozilla.org/security/advisories/mfsa2025-14/
https://www.mozilla.org/security/advisories/mfsa2025-16/
https://www.mozilla.org/security/advisories/mfsa2025-17/
https://www.mozilla.org/security/advisories/mfsa2025-18/
https://lists.debian.org/debian-lts-announce/2025/03/msg00006.html

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