Mozilla developers and community identified and fixed several memory safety bugs in the browser engine used in Firefox and other Mozilla-based products. Some of these bugs showed evidence of memory corruption under certain circumstances, and we presume that with enough effort at least some of these could be exploited to run arbitrary code.
Andrew Osmond, Olli Pettay, Andrew Sutherland, Christian Holler, David Major, Andrew McCreight and Cameron McCormack reported memory safety problems and crashes that affect Firefox ESR 38.2 and Firefox 40.
Bob Clary and Randell Jesup reported crash and memory safety problems that affect Firefox 40.