PS fluid leak on reservoir fill

[RiverRatMatt]

I noticed there was a small amount of power steering fluid that had leaked out of the fill cap on my 2010. It was just enough to coat the top of the fill canister. Any idea what would cause this?

 

[Jacket]

Have you done anything to the PS system lately? Top off fluid? Could it be overfilled? Did you do any aggressive back and forth steering that may have bubbled up some air?