Related Vulnerabilities: CVE-2021-29957  

If a MIME encoded email contains an OpenPGP inline signed or encrypted message part, but also contains an additional unprotected part, Thunderbird did not indicate that only parts of the message are protected. This vulnerability affects Thunderbird < 78.10.2.

Severity Low

Remote Yes

Type Content spoofing

Description

If a MIME encoded email contains an OpenPGP inline signed or encrypted message part, but also contains an additional unprotected part, Thunderbird did not indicate that only parts of the message are protected. This vulnerability affects Thunderbird < 78.10.2.

AVG-1964 thunderbird 78.10.1-1 Low Vulnerable

https://www.mozilla.org/security/advisories/mfsa2021-22/
https://bugzilla.mozilla.org/show_bug.cgi?id=1673241