Security Vulnerabilities fixed in Thunderbird 91.4.1 — Mozilla

When receiving an OpenPGP/MIME signed email message that contains an additional outer MIME message layer, for example a message footer added by a mailing list gateway, Thunderbird only considered the inner signed message for the signature validity. This gave the false impression that the additional contents were also covered by the digital signature. Starting with Thunderbird version 91.4.1, only the signature that belongs to the top level MIME part will be considered for the displayed status.
Thunderbird users who use the Matrix chat protocol were vulnerable to a buffer overflow in libolm, that an attacker may trigger by a crafted sequence of messages. The overflow content is partially controllable by the attacker and limited to ASCII spaces and digits.