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)

EPSS: 0.003 (25.3th percentile) — read the EPSS interpretation.

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.

Affected products

Mozilla Firefox — versions 143
Mozilla Thunderbird — versions 143

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

Public proof-of-concept exploits

References

security@mozilla.org (Permissions Required)
security@mozilla.org (Vendor Advisory)
security@mozilla.org (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.