With firefox global menu bar integration activated in kubuntu/unity7 dropdown menus don't work

[Ray-Ven]

If firefox-globalmenu is activated in add-ons after a uncertain time, dropdown menues don't stay open anymore.
for Example: In Addon-Tab "look for updates" cannot be chosen anymore because the menu closes immediately.
It seems, that it doesn't happen without firefox-globalmenu activated.
Maybe it's related to KDE somehow? Maybe it doesn't affect non-KDE-users.
This happens with new created firefox-profiles too. (don't know how the menubar integration came in there anyway, KDEusers don't need it)

[Korepwx (public-c)]

Here I've also came across in this bug, and I made a screen shot about it.

http://www.youtube.com/watch?v=b7v91b_7-xU

Furthormore, I tried to disable global menu bar in plasma, but let the app menus to be "shown in title bar as a button" (which is a feature by KDE). The bug also appeared.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Rudra Saraswat (rs2009)]

I've edited the title to include Unity7 as well.