It is possible to delete an IndexedDB key value and subsequently try to extract it during conversion. This results in a use-after-free and a potentially exploitable crash. This vulnerability affects Firefox < 69, Thunderbird < 68.1, Thunderbird < 60.9, Firefox ESR < 60.9, and Firefox ESR < 68.1.
https://usn.ubuntu.com/4150-1/
https://security.gentoo.org/glsa/201911-07
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00017.html
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00011.html
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00010.html
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00009.html