Tfc-2020

**Name of the Vulnerable Software and Affected Versions** Firefox versions prior to 82.0.3 Firefox ESR versions prior to 78.4.1 Thunderbird versions prior to 78.4.2 **Description** The issue is related to the MCallGetProperty opcode being emitted with unmet assumptions, resulting in an exploitable use-after-free condition. This can lead to accessing already freed memory, which is suitable for creating a working exploit. The problem is associated with the incorrect usage of the MCallGetProperty operation code. **Recommendations** For Firefox versions prior to 82.0.3, update to version 82.0.3 or later. For Firefox ESR versions prior to 78.4.1, update to version 78.4.1 or later. For Thunderbird versions prior to 78.4.2, update to version 78.4.2 or later.