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.
Disable JavaScript until a version containing these fixes can be installed.
Henri Sivonen, Boris Zbarsky, Zack Weinberg, Bob Clary, Martijn Wargers, and Paul Nickerson reported crashes in the browser engine.