The JavaScript engine in Mozilla Firefox before 3.0.11, Thunderbird before 2.0.0.22, and SeaMonkey before 1.1.17 allows remote attackers to cause a denial of service (memory corruption and application crash) or possibly execute arbitrary code via vectors related to (1) js_LeaveSharpObject, (2) ParseXMLSource, and (3) a certain assertion in jsinterp.c; and other vectors.