Secret is a secret. If someone trusts me enough to share it with me then I should respect that & keep it to myself. Even if later on I am not in good terms with that person I still don't spill it out. In my views that's the most disgusting thing a person can do.
Gossiping on the other hand is different. That's just gunnah man. I try to stay away from that as much as I can.
P.s A secret remains a secret only when it is in your heart, once it is revealed it spreads like fire in the woods.
Agree with TLK as well though. It sometimes depends on the secret too.