So I just replaced all the brakes - pads, rotors, wheel cylinders, shoes, and hardware and bled the system (I had a leaky wheel cylinder.) Brakes work much better now. Great.

Now, this morning, I happened to be looking under the hood and I notice that the brake power booster and engine compartment below the master cylinder is all wet. Inside the reservoir, the level has shot way up past the "full" line and the whole thing's basically full of fluid except for some pockets of air.

Is this a leaking master cylinder? What should I do?

 

I should add I haven't noticed any difference in braking power.