The browser engine in Mozilla Firefox 3.0.x before 3.0.18 and 3.5.x before 3.5.8, 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) or possibly execute arbitrary code via vectors related to the nsBlockFrame::StealFrame function in layout/generic/nsBlockFrame.cpp, and unspecified other vectors.