It was discovered that Thunderbird didn’t ignore IMAP server responses
prior to completion of the STARTTLS handshake. A person-in-the-middle
could potentially exploit this to trick Thunderbird into showing incorrect
information. (CVE-2021-29969)
Multiple security issues were discovered in Thunderbird. If a user were
tricked into opening a specially crafted website in a browsing context, an
attacker could potentially exploit these to cause a denial of service, or
execute arbitrary code. (CVE-2021-29970, CVE-2021-29976, CVE-2021-29980,
CVE-2021-29984, CVE-2021-29985, CVE-2021-29986, CVE-2021-29988,
CVE-2021-29989, CVE-2021-30547)
ubuntu.com/security/CVE-2021-29969
ubuntu.com/security/CVE-2021-29970
ubuntu.com/security/CVE-2021-29976
ubuntu.com/security/CVE-2021-29980
ubuntu.com/security/CVE-2021-29984
ubuntu.com/security/CVE-2021-29985
ubuntu.com/security/CVE-2021-29986
ubuntu.com/security/CVE-2021-29988
ubuntu.com/security/CVE-2021-29989
ubuntu.com/security/CVE-2021-30547
ubuntu.com/security/notices/USN-5058-1