Many websites or webapps(for example twitter website) hijack the keyboard strokes as keyboard shortcuts in their web page. And in many cases some of the shortcuts conflict with the system-based keyboard shortcuts. Since firefox enable user to "disable javascript to hijack context menu" at: Tools/Options/Content/Enable Javascript Advanced/Disable or replace context menus Why don't you add the feature to "disable javascript to hijack keyboard shortcuts"? Just a checkbox at: Tools/Options/Content/Enable Javascript Advanced/Catch keyboard events

Not a security bug.

Look at the discussions: http://superuser.com/questions/337108/how-can-i-disable-arrow-key-hijacking-on-websites http://superuser.com/questions/168087/how-to-forbid-keyboard-shortcut-stealing-by-websites-in-firefox