Mystery leak from brake caliper. What to do? I had poor performance from my SRAM Apex hydraulic disk brakes. This weekend, I bled them, and it seemed to solve the problem. However, on my next ride, I decided to test the newly bled brakes with a particularly hard stop. When I did so, I saw a puff of smoke. I assumed that it was oil on the hot rotor, so I looked closer. Sure enough, when I pump the front brake hard, a little oil runs down the disc. Also, the lever is almost as soft as before I bled the brakes. At least the rear brake seems fine.

At this point, I'm not sure what to do. I know the disc needs to be cleaned and the pads need to be replaced, but I do not know how to fix the leak. I don't even know where the leak is coming from, because the bleed port and cable are dry on the outside. 

A couple of questions: 
First, where could it be leaking from? Could it be from around the pistons? If so, how would you fix it?
Second, could this be fixed under warranty? I assume it would be SRAM warranty, not Planet X, right? The bike is almost brand new. If so, how would I go about that? Do I take it to my LBS? The bike was bought online. Please help.

I miss the cheap and simple mechanical discs from my last bike.
Sounds like a bad piston seal to me. Could also be any seal from around the calliper area, split line, cracked calliper.

Assuming these are newish and you've not bashed them up this should be a warranty claim. This will almost always have to go through the place you bought the bike, but there are exceptions.

You should email SRAM, the maker, and the shop to see who wants it back and see if the whole bike needs to be retuned or just the failed brake.