To reproduce (Firefox):
# Go to phabricator home page.
# Open explorer window
# start dragging files, drag over browser windows
# drag out of browser window again
# watch phabricator being stuck with the "Drop Files to Upload" overlay with no way to close it anymore
It seems that no "hover-out"-like event is generated/handled. Also, does it make sense to just drag-n-drop anything all the time? I think it could be a source of problems, if someone accidentally drops something confidential while working with other windows that cover parts of the browser window.