Does anybody know what holds the rear fender liners flush with the body?

My drivers side rear are coming detached from the fender and hitting the tire on large bumps.

If if it's an easy fix I'd prefer to avoid a trip to the dealer.

 

interesting...no screw holes? On my XF the screws had a habit of falling out over time. Turned in the car at end of lease with no screws in place. Somehow the body seemed to have a natural "groove" on the inside that they fit into as well.