Mozilla developers 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.
In general these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled, but are potentially a risk in browser or browser-like contexts.
Christoph Diehl, Christian Holler, Jesse Ruderman, Timothy Nikkel, and Jeff Walden reported memory safety problems and crashes that affect Firefox ESR 17, and Firefox 20.
Bob Clary, Ben Turner, Benoit Jacob, Bobby Holley, Christoph Diehl, Christian Holler, Andrew McCreight, Gary Kwong, Jason Orendorff, Jesse Ruderman, Matt Wobensmith, and Mats Palmgren reported memory safety problems and crashes that affect Firefox 20.