Memory safety bugs present in Firefox 60 and Firefox ESR 60. Some of these bugs showed evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code. This vulnerability affects Thunderbird < 60, Firefox ESR < 60.1, and Firefox < 61.
https://www.mozilla.org/security/advisories/mfsa2018-19/
https://www.mozilla.org/security/advisories/mfsa2018-16/
https://www.mozilla.org/security/advisories/mfsa2018-15/
https://www.debian.org/security/2018/dsa-4295
https://usn.ubuntu.com/3705-1/
https://security.gentoo.org/glsa/201811-13
https://security.gentoo.org/glsa/201810-01
https://lists.debian.org/debian-lts-announce/2018/11/msg00011.html