The Mozilla Updater can be made to choose an arbitrary target working directory for output files resulting from the update process. This vulnerability requires local system access. Note: this issue only affects Windows operating systems. This vulnerability affects Thunderbird < 45.5, Firefox ESR < 45.5, and Firefox < 50.
https://www.mozilla.org/security/advisories/mfsa2016-93/
https://www.mozilla.org/security/advisories/mfsa2016-90/
https://www.mozilla.org/security/advisories/mfsa2016-89/
https://security.gentoo.org/glsa/201701-15