Mozilla developers identified and fixed several stability bugs in the browser engine used in Firefox and other Mozilla-based products. Some of these crashes 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.
Martijn Wargers, Josh Soref, and Jesse Ruderman reported crashes in the browser engine that affected Firefox 3.5 and Firefox 3.6.
Jesse Ruderman and Ehsan Akhgari reported crashes that affected all supported versions of the browser engine.