Memory safety bugs were reported in Firefox 59, Firefox ESR 52.7, and Thunderbird 52.7. 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 < 52.8, Thunderbird ESR < 52.8, Firefox < 60, and Firefox ESR < 52.8.
https://www.mozilla.org/security/advisories/mfsa2018-13/
https://www.mozilla.org/security/advisories/mfsa2018-12/
https://www.mozilla.org/security/advisories/mfsa2018-11/
https://www.debian.org/security/2018/dsa-4209
https://www.debian.org/security/2018/dsa-4199
https://usn.ubuntu.com/3688-1/
https://usn.ubuntu.com/3660-1/
https://usn.ubuntu.com/3645-1/
https://security.gentoo.org/glsa/201811-13
https://security.gentoo.org/glsa/201810-01
https://lists.debian.org/debian-lts-announce/2018/05/msg00013.html
https://lists.debian.org/debian-lts-announce/2018/05/msg00007.html
https://access.redhat.com/errata/RHSA-2018:1726
https://access.redhat.com/errata/RHSA-2018:1725
https://access.redhat.com/errata/RHSA-2018:1415
https://access.redhat.com/errata/RHSA-2018:1414