That doesn't exactly look like what I would call a leak.
Grime off the road from tyres and even from your own vehicles "Grease-Points" can collect dust & dirt and then accumulate in all sorts of little "Nook & Cranny" type places and that is what your pictures are showing me.
Unless I am missing something in the pics, then you have nothing to worry about except for the possibility that you might wanna get some paper towel and do a bit of a wipe down.
Ooh, Ahh, if you are into doing this kinda wipe down then mine could REALLY do with your help.