CVE 2016-5290
Memory safety bugs were reported in Firefox 49 and Firefox ESR 45.4. 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 < 45.5, Firefox ESR < 45.5, and Firefox < 50.
See the 
CVE page on Mitre.org
for more details.
