Multiple unspecified vulnerabilities in Mozilla Firefox before 2.0.0.17 and 3.x before 3.0.2, Thunderbird before 2.0.0.17, and SeaMonkey before 1.1.12 allow remote attackers to cause a denial of service (memory corruption and application crash) or possibly execute arbitrary code via vectors related to the JavaScript engine and (1) misinterpretation of the characteristics of Namespace and QName in jsxml.c, (2) misuse of signed integers in the nsEscapeCount function in nsEscape.cpp, and (3) interaction of JavaScript garbage collection with certain use of an NPObject in the nsNPObjWrapper::GetNewOrUsed function in nsJSNPRuntime.cpp.