CVE-2026-16396 is a privilege escalation vulnerability within the WebExtensions component of Mozilla Firefox. This flaw allows an attacker to gain elevated privileges, potentially compromising the security boundaries intended by the browser. The issue was fixed in Firefox 153 and Firefox ESR 140.13. The CVSS v3.1 base score is 8.8 (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H), indicating that the vulnerability can be exploited remotely with low attack complexity, no privileges required, but user interaction is needed. Successful exploitation could lead to full compromise of confidentiality, integrity, and availability of the affected system. Mozilla's official advisories confirm the fix and recommend upgrading to the patched versions.

The vulnerability allows an attacker to escalate privileges within the Firefox WebExtensions environment, potentially enabling unauthorized actions or access to sensitive data. The CVSS score of 8.8 reflects high impact on confidentiality, integrity, and availability. However, there are no reports of active exploitation in the wild at this time. Exploitation requires user interaction but no prior privileges, making it a significant risk for users running affected versions.

Mozilla has released official fixes for this vulnerability in Firefox 153 and Firefox ESR 140.13. Users and administrators should upgrade to these versions or later to remediate the issue. Since this is not a cloud service, patching the client software is necessary. No additional mitigation steps are indicated by the vendor advisory.