ATF In The Brake System?

[Dzchey21]

its very possible for the brake booster to leak, and force oil into the master cylinder. its kinda odd and not very common since it has to pass thru 2 seals but that is littlerally the only place it can happen. I would replace both the booster and the master cylinder. Then i would pull the bleeder and see if atf has actually made it down to the calipers ect, i doubt that it has the oil stays pretty stagnant in the lines to everything since they basically work back and forth like a see saw and not really flow from the caliper back to the master cylinder