The browser engine in Mozilla Firefox 3.0.x before 3.0.18, 3.5.x before 3.5.8, and 3.6.x before 3.6.2; Thunderbird before 3.0.2; and SeaMonkey before 2.0.3 allows remote attackers to cause a denial of service (memory corruption and application crash) and possibly execute arbitrary code via vectors related to (1) layout/generic/nsBlockFrame.cpp and (2) the _evaluate function in modules/plugin/base/src/nsNPAPIPlugin.cpp.