When browsing a malicious page, a race condition in our SharedWorkerService could occur and lead to a potentially exploitable crash. This vulnerability affects Thunderbird < 68.9.0, Firefox < 77, and Firefox ESR < 68.9.
https://www.mozilla.org/security/advisories/mfsa2020-22/
https://www.mozilla.org/security/advisories/mfsa2020-21/
https://www.mozilla.org/security/advisories/mfsa2020-20/