CVE-2025-10859: Vulnerability in Mozilla Firefox for iOS
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.
AI Analysis
Technical Summary
This vulnerability involves improper isolation of cookie storage between private (Incognito) tabs and normal browsing tabs in Firefox for iOS. Specifically, cookies for non-HTML temporary documents were shared incorrectly, allowing data from private browsing sessions to leak into normal sessions after private tabs were closed. This undermines the privacy guarantees of Incognito mode. Mozilla fixed this issue in Firefox for iOS version 143.1 as documented in their security advisory MFSA2025-79.
Potential Impact
The vulnerability allows leakage of data stored in cookies from private browsing sessions to normal browsing sessions after private tabs are closed. This compromises user privacy by exposing information that should have been isolated within Incognito mode. The impact is limited to confidentiality with no reported effects on integrity or availability. There are no known active exploits targeting this vulnerability.
Mitigation Recommendations
Users should update to Firefox for iOS version 143.1 or later, where this vulnerability has been fixed. Applying this official patch fully mitigates the issue. No additional mitigation steps are required beyond updating to the fixed version.
CVE-2025-10859: Vulnerability in Mozilla Firefox for iOS
Description
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.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability involves improper isolation of cookie storage between private (Incognito) tabs and normal browsing tabs in Firefox for iOS. Specifically, cookies for non-HTML temporary documents were shared incorrectly, allowing data from private browsing sessions to leak into normal sessions after private tabs were closed. This undermines the privacy guarantees of Incognito mode. Mozilla fixed this issue in Firefox for iOS version 143.1 as documented in their security advisory MFSA2025-79.
Potential Impact
The vulnerability allows leakage of data stored in cookies from private browsing sessions to normal browsing sessions after private tabs are closed. This compromises user privacy by exposing information that should have been isolated within Incognito mode. The impact is limited to confidentiality with no reported effects on integrity or availability. There are no known active exploits targeting this vulnerability.
Mitigation Recommendations
Users should update to Firefox for iOS version 143.1 or later, where this vulnerability has been fixed. Applying this official patch fully mitigates the issue. No additional mitigation steps are required beyond updating to the fixed version.
Technical Details
- Data Version
- 5.1
- Assigner Short Name
- mozilla
- Date Reserved
- 2025-09-22T18:14:38.909Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 68dc71325d588c52e5de478d
Added to database: 10/1/2025, 12:09:22 AM
Last enriched: 4/14/2026, 11:34:40 AM
Last updated: 5/10/2026, 8:11:53 AM
Views: 242
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