Security Vulnerabilities fixed in Thunderbird 78.2 — Mozilla

If Thunderbird is installed to a user-writable directory, the Mozilla Maintenance Service would execute updater.exe from the install location with system privileges. Although the Mozilla Maintenance Service does ensure that updater.exe is signed by Mozilla, the version could have been rolled back to a previous version which would have allowed exploitation of an older bug and arbitrary code execution with System Privileges.Note: This issue only affected Windows operating systems. Other operating systems are unaffected.
By holding a reference to the eval() function from an about:blank window, a malicious webpage could have gained access to the InstallTrigger object which would allow them to prompt the user to install an extension. Combined with user confusion, this could result in an unintended or malicious extension being installed.
Mozilla developers Jason Kratzer, Christian Holler, Byron Campen, Tyson Smith reported memory safety bugs present in Thunderbird 78.1. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code.