Double sided 3M foam tape - the sooner its removed the better as you may have paint fade underneath. More than likely not though.
Again due to length and use there may be some small scratches around the lip of your fenders due to crap getting behind the fender flares, but you should be ok.
Use a 3M eraser wheel or goo gone and lots of elbow grease to get that tape/residue off.
My local Napa carries the 3m wheels.
Would they remove the 4x4 decals on the rear 1/4's?