2003 Chevy Malibu leak of fluid

Hi. I have a small leak in the rear of the vehicle. It leaves a puddle about the size of an oil leak, if there was one located in the front.

But this leak is in the rear between the muffler and the tail pipe. It doesn't feel like oil, however, it's not water because it bubbles up like oil when it hits wet ground. There is no odor.

I just can't figure out what in the world it could be and would appreciate any knowledge you may have on this subject. Thanks very much. Robyn