Hi
I have the same problem.
A normal member (Registered) invited to a group gets the options of an Owner, they can delete , edit etc the group.
These options even appear when they simply view the menu on the Invite and even at this stage it gives them delete etc options even without joining the group.
Attached 2 images and any help on how to fix, or address, this are greatly appreciated, thanks.
Joomla 2.5.11
CB 1.9
Groupjive 2.61 and problem still happening on upgrade to 2.7