If Thunderbird is configured to use STARTTLS for an IMAP server, and the server sends a PREAUTH response, then Thunderbird will continue with an unencrypted connection, causing email data to be sent without protection. This vulnerability affects Thunderbird < 68.9.0.
1:68.10.0+build1-0ubuntu0.16.04.11:68.10.0+build1-0ubuntu0.18.04.11:68.10.0+build1-0ubuntu0.20.04.1Exploitability
AV:NAC:LPR:NUI:NScope
S:UImpact
C:HI:NA:NCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N