A use-after-free vulnerability with content viewer listeners that results in a potentially exploitable crash. This vulnerability affects Firefox < 54, Firefox ESR < 52.2, and Thunderbird < 52.2.
bugzilla.redhat.com/show_bug.cgi?id=1461255
www.mozilla.org/en-US/security/advisories/mfsa2017-16/#CVE-2017-7751