Vulnerability in Mozilla Firefox
CVE-2025-10859
Cookie storage for non-HTML temporary documents was being shared incorrectly with normal browsing content, allowing information from private tabs to escape Incognito mode even after the user closed all tabs. This vulnerability was fixed in Firefox for iOS 143.1.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.0 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.
EPSS exploit prediction
EPSS: 0.001 (1.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 2nd percentile — 1.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.001 · newest: 0.001 · change: +0.000
Affected products
- Mozilla Firefox
- Mozilla Firefox For iOS — versions 143.1
Weakness classification (CWE)
Public proof-of-concept exploits
References
- bugzilla.mozilla.org/show_bug.cgi (Permissions Required, Issue Tracking)
- www.mozilla.org/security/advisories/mfsa2025-79/ (Vendor Advisory)
Frequently asked questions
- What is CVE-2025-10859?
- CVE-2025-10859 is a medium-severity vulnerability in Mozilla Firefox, classified under Exposure of Private Personal Information to an Unauthorized Actor. CVSS score: 4.0/10. Published 2025-09-30.
- How severe is CVE-2025-10859?
- Medium severity. CVSS v3 base score is 4.0 out of 10.
- Is CVE-2025-10859 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.