The nsTableFrame::InsertFrames function in Mozilla Firefox 4.x through 13.0, Firefox ESR 10.x before 10.0.6, Thunderbird 5.0 through 13.0, Thunderbird ESR 10.x before 10.0.6, and SeaMonkey before 2.11 does not properly perform a cast of a frame variable during processing of mixed row-group and column-group frames, which might allow remote attackers to execute arbitrary code via a crafted web site.