Big Online Reality TV Shows are able to keep the winner names a secret even after the shooting is finished. Even after searching on the Internet one is not able to find them. How do they keep such things confidential when there are huge audiences present?
I had a friend who was on a baking competition show. He was required to sign a non-disclosure agreement saying that he would not reveal the winners or losers of the show until the episode had aired. There was some penalty if he did reveal anything, though I don't recall what it was. Surely if he had won (he didn't) they would have revoked his winnings.
On the up side, the day it aired, he baked several of the things he made on the show and we ate them while we watched the competition!