Executive brief
Firefox's Profile Backup feature contains a sandbox escape vulnerability that allows an attacker to break out of the browser's security sandbox and execute code with elevated privileges. This could lead to unauthorized access to user data, installation of malware, or full system compromise. The vulnerability affects Firefox versions prior to 156 and has been patched.
Technical details
This is a sandbox escape vulnerability in the Profile Backup component of Firefox. The attack is reachable over the network and does not require authentication or user interaction beyond normal browser usage. A successful exploit breaks the browser sandbox, allowing an attacker to execute arbitrary code outside the restricted execution environment. This could enable theft of sensitive data stored in user profiles or system-level attacks. The vulnerability has been fixed in Firefox 156 and Thunderbird 156.
Affected products
- Mozilla Firefox before 156
- Mozilla Thunderbird before 156
Timeline
- 2026-09-15: disclosed
- 2026-09-15: patched: Fixed in Firefox 156 and Thunderbird 156