CVE-2026-74983 is a mitigation bypass vulnerability affecting the Data Loss Prevention component in Mozilla Firefox. It was internally discovered and fixed in Firefox 154 and corresponding ESR and Thunderbird versions. The vulnerability has a CVSS 3.1 score of 8.1 (high severity) with network attack vector, low attack complexity, no privileges required, user interaction required, and impacts confidentiality and integrity. The vendor advisory confirms the fix is available in Firefox 154 and ESR 140.14 and 153.1. No active exploitation is reported.

The vulnerability allows an attacker to bypass mitigation controls in the Data Loss Prevention component, potentially leading to unauthorized access or leakage of sensitive data. The CVSS score indicates high impact on confidentiality and integrity. However, there are no known exploits in the wild at this time.

A fix is available and users should upgrade to Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, or Thunderbird 153.1 to remediate this vulnerability. No additional action is required beyond applying these official updates.