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 and SeaMonkey products because scripting is disabled, but are potentially a risk in browser or browser-like contexts in those products.
Olli Pettay, Christoph Diehl, Gary Kwong, Jesse Ruderman, Andrew McCreight, Joe Drew, and Wayne Mery reported memory safety problems and crashes that affect Firefox ESR 17, and Firefox 18.
Alon Zakai, Christian Holler, Gary Kwong, Jesse Ruderman, Luke Wagner, Terrence Cole, Timothy Nikkel, Olli Pettay, Bill McCloskey, and Nicolas Pierron reported memory safety problems and crashes that affect Firefox 18.