Comment 25 for bug 1020198

it also appears with KDE’s plasma-widget-menubar: as soon as the menu it operated the first time after restarting firefox, all popups break in the described way (only flickering into view once instead of staying open).

makes using bookmarks almost impossible as you have to go over the menu, and, since middle click in the dbus menu doesn’t work, you also have to open a new tab beforehand if you want the bookmark in a new tab. pretty annoying :/