Note: There was another topic somewhat similar to this one, but it had a different focus.
I have a bad habit of picking up unowned groups whether I need them or not, and I have recently come across a group that is effectively unusable due to this bug.
The “Guest” role in this group has access to almost every possible permission, and I have no way to turn it off due to the removal of the ability to edit most Guest permissions.
The bug occurs on all groups that gave Guests extra permissions prior to the update. This group is a good example.
I believe the best course of action to fix this is to simply retroactively disable all unconfigurable Guest permissions.