Multiple unspecified vulnerabilities in the browser engine in Mozilla Firefox before 13.0, Thunderbird before 13.0, and SeaMonkey before 2.10 allow remote attackers to cause a denial of service (memory corruption and application crash) or possibly execute arbitrary code via vectors related to (1) methodjit/ImmutableSync.cpp, (2) the JSObject::makeDenseArraySlow function in js/src/jsarray.cpp, and unknown other components.