When using nested workers, a use-after-free could occur during worker destruction. This resulted in a potentially exploitable crash. This vulnerability affects Thunderbird < 68.3, Firefox ESR < 68.3, and Firefox < 71.
https://usn.ubuntu.com/4335-1/
https://usn.ubuntu.com/4241-1/
https://security.gentoo.org/glsa/202003-10
https://security.gentoo.org/glsa/202003-02
https://access.redhat.com/errata/RHSA-2020:0295
https://access.redhat.com/errata/RHSA-2020:0292
http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00001.html
http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00000.html