Multiple security issues were discovered in Thunderbird, which could
result in the execution of arbitrary code, spoofing, information disclosure, downgrade attacks on SMTP STARTTLS connections or misleading display of OpenPGP/MIME signatures.
For the oldstable distribution (buster), these problems have been fixed
in version 1:91.4.1-1~deb10u1.
For the stable distribution (bullseye), these problems have been fixed in version 1:91.4.1-1~deb11u1.
We recommend that you upgrade your thunderbird packages.