Mozilla has published a security advisory, highlighting a vulnerability in the following product listed below on the 6th of October 2021. It is recommended that you take the necessary precautions by ensuring your product are always updated.
For more information on this update, you can follow this URL:
https://www.mozilla.org/en-US/security/advisories/mfsa2021-47/
The Guyana National CIRT recommends that users and administrators review this update and apply it where necessary.
PDF Download: Mozilla Security Advisory for Thunderbird.pdf
References
https://www.mozilla.org/en-US/security/advisories/mfsa2021-47/
https://www.cyber.gc.ca/en/alerts/mozilla-security-advisory-46