The PreserveWrapper implementation in Mozilla Firefox before 22.0, Firefox ESR 17.x before 17.0.7, Thunderbird before 17.0.7, and Thunderbird ESR 17.x before 17.0.7 does not properly handle the lack of a wrapper, which allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code by leveraging unintended clearing of the wrapper cache's preserved-wrapper flag.