The focus handling for the onkeydown event in Mozilla Firefox 1.5.0.12, 2.0.0.4 and other versions before 2.0.0.8, and SeaMonkey before 1.1.5 allows remote attackers to change field focus and copy keystrokes via the "for" attribute in a label, which bypasses the focus prevention, as demonstrated by changing focus from a textarea to a file upload field.