XSS in Mozilla Firefox
CVE-2025-1935
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.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N.
EPSS exploit prediction
EPSS: 0.003 (25.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 25th percentile — 25.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000
Affected products
- Mozilla Firefox — versions 128.8, 136
- Mozilla Thunderbird — versions 128.8, 136
Weakness classification (CWE)
Public proof-of-concept exploits
References
- bugzilla.mozilla.org/show_bug.cgi (Issue Tracking)
- www.mozilla.org/security/advisories/mfsa2025-14/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-16/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-17/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-18/ (Vendor Advisory)
- af854a3a-2127-422b-91ae-364da2661108
Frequently asked questions
- What is CVE-2025-1935?
- CVE-2025-1935 is a medium-severity vulnerability in Mozilla Firefox, classified under Cross-site Scripting. CVSS score: 4.3/10. Published 2025-03-04.
- How severe is CVE-2025-1935?
- Medium severity. CVSS v3 base score is 4.3 out of 10.
- Is CVE-2025-1935 known to be exploited?
- 3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.