A local attacker can trick the Mozilla Maintenance Service into applying an unsigned update file by pointing the service at an update file on a malicious SMB server. The update file can be replaced after the signature check, before the use, because the write-lock requested by the service does not work on a SMB server. *Note: This attack requires local system access and only affects Windows. Other operating systems are not affected.* This vulnerability affects Firefox < 112, Firefox ESR < 102.10, and Thunderbird < 102.10.