Mozilla developers 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.
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-3651
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-3652
cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-3654
bugzilla.mozilla.org/buglist.cgi?bug_id=646968,652054,665070,671160,672892,674843,675515,676918,677847,679593,686044
bugzilla.mozilla.org/show_bug.cgi?id=682727
bugzilla.mozilla.org/show_bug.cgi?id=694953