NPAPI plugins, such as Adobe Flash, can send non-simple cross-origin requests, bypassing CORS by making a same-origin POST that does a 307 redirect to the target site. This allows for a malicious site to engage in cross-site request forgery (CSRF) attacks. This vulnerability affects Thunderbird < 60, Thunderbird < 52.9, Firefox ESR < 60.1, Firefox ESR < 52.9, and Firefox < 61.
https://www.mozilla.org/security/advisories/mfsa2018-19/
https://www.mozilla.org/security/advisories/mfsa2018-18/
https://www.mozilla.org/security/advisories/mfsa2018-17/
https://www.mozilla.org/security/advisories/mfsa2018-16/
https://www.mozilla.org/security/advisories/mfsa2018-15/
https://www.debian.org/security/2018/dsa-4244
https://www.debian.org/security/2018/dsa-4235
https://usn.ubuntu.com/3714-1/
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/2018/07/msg00013.html
https://lists.debian.org/debian-lts-announce/2018/06/msg00014.html
https://bugzilla.mozilla.org/show_bug.cgi?id=1436241
https://access.redhat.com/errata/RHSA-2018:2252
https://access.redhat.com/errata/RHSA-2018:2251
https://access.redhat.com/errata/RHSA-2018:2113
https://access.redhat.com/errata/RHSA-2018:2112