STR (according to bug 1071302): 1) Open about:config and set dom.popup_allowed_events to "" 2) View some Bugzilla bug, and choose to add an attachment 3 [review]) Click on "Browse" to open the file input dialog ER: Native file input dialog should open. AR: No dialog, and no user feedback about why. Now, I know that the likely reaction to "Doctor, it hurts when I do X" is "Well, don't do X!" - so the user should probably not have set dom.popup_allowed_events to ""... but it strikes me as odd that we'd somehow equate the file input dialog with a traditional dialog. That seems like a mistake, and an unnecessary footgun.

Happens here on Linux Firefox 32.0.2 (mozilla.org version) with the gtk-filechooser, too. Not only for empty string, but for removing the "click" and "mousedown" events, too. I think widgets, which are part of other widgets should not suffer from this restriction and popups, which belong to xul or even native dialogs should not be restricted, too.