Leak at right bumper of car

I noticed a leak yesterday dripping from a bolt that attaches the bumper to the car. This is located on the right rear bumper. I looked with a flashlight and can only see it coming from the bumper and no other fluid streams coming from tire area. The fluid is yellow and seems clean when I touch it from the bolt its dripping from. What can possibly leak from the bumper alone? I checked my fluids under the hood and everything seems okay.

My car is a 1998 Nissan Altima.

Thanks,

rosy:confused:

Um. I fixed the problem. I threw away the crack quart of oil that was in the trunk compartment on the side. Thanks for looking. Maybe this will be helpful in the future.