Security Vulnerabilities fixed in Thunderbird 91.2 — Mozilla

Thunderbird ignored the configuration to require STARTTLS security for an SMTP connection. A MITM could perform a downgrade attack to intercept transmitted messages, or could take control of the authenticated session to execute SMTP commands chosen by the MITM. If an unprotected authentication method was configured, the MITM could obtain the authentication credentials, too.
During operations on MessageTasks, a task may have been removed while it was still scheduled, resulting in memory corruption and a potentially exploitable crash.
Through use of reportValidity() and window.open(), a plain-text validation message could have been overlaid on another origin, leading to possible user confusion and spoofing attacks.
During process shutdown, a document could have caused a use-after-free of a languages service object, leading to memory corruption and a potentially exploitable crash.
In the crossbeam crate, one or more tasks in the worker queue could have been be popped twice instead of other tasks that are forgotten and never popped. If tasks are allocated on the heap, this could have caused a double free and a memory leak.
Mozilla developers and community members Andreas Pehrson and Christian Holler reported memory safety bugs present in Thunderbird 91.1. 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.
Mozilla developers and community members Kevin Brosnan, Mihai Alexandru Michis, and Christian Holler reported memory safety bugs present in Thunderbird 91.1. 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.