I don't have Membership installed, but..

I don't have Membership installed on the site in question, but I see a section in the 'Edit User' page with the heading 'Additional Capabilities' and the sub-heading 'Capabilities' - the rest is empty.

What could cause this?

EDIT: Whoops, my mistake. Looks like a new thing that's baked into WP itself. Ignore this please!