# CVE-2026-92066: Mozilla Firefox sandbox escape in Profile Backup

Source: https://junglewise.ai/threats/cve-2026-92066-mozilla-firefox-sandbox-escape-in-profile-backup  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-15. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-92066 · Severity: critical · CVSS 9.8 · Published 2026-09-15

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.

Technologies: [Mozilla Firefox](https://junglewise.ai/threats/technologies/firefox), [Mozilla Thunderbird](https://junglewise.ai/threats/technologies/thunderbird). Vendors: [Mozilla](https://junglewise.ai/threats/vendors/mozilla).

## Quick answers

**Is CVE-2026-92066 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-92066 being exploited in the wild.

**How severe is CVE-2026-92066?** Critical severity, with a CVSS score of 9.8, published 15 September 2026.

**Which products and versions are affected?** Mozilla Firefox before 156; Mozilla Thunderbird before 156.

**Is there a fix for CVE-2026-92066?** A patch was published on 2026-09-15: Fixed in Firefox 156 and Thunderbird 156 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-92066 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-92066?** Check whether you run Mozilla Firefox or Mozilla Thunderbird at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## 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

## References

- [https://bugzilla.mozilla.org/show_bug.cgi?id=2058093](https://bugzilla.mozilla.org/show_bug.cgi?id=2058093)
- [https://www.mozilla.org/security/advisories/mfsa2026-90/](https://www.mozilla.org/security/advisories/mfsa2026-90/)

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