XSS in Mozilla Firefox
CVE-2025-10534
Spoofing issue in the Site Permissions component. This vulnerability was fixed in Firefox 143 and Thunderbird 143.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (26.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 26th percentile — 26.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Mozilla Firefox — versions 143
- Mozilla Thunderbird — versions 143
Weakness classification (CWE)
Public proof-of-concept exploits
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
- www.mozilla.org/security/advisories/mfsa2025-73/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2025-77/ (Vendor Advisory)
Frequently asked questions
- What is CVE-2025-10534?
- CVE-2025-10534 is a high-severity vulnerability in Mozilla Firefox, classified under Cross-site Scripting. CVSS score: 8.1/10. Published 2025-09-16.
- How severe is CVE-2025-10534?
- High severity. CVSS v3 base score is 8.1 out of 10.
- Is CVE-2025-10534 known to be exploited?
- 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.