Would you call out a friend for their infidelity?

So I was randomly thinking. What if you had a friend who was cheating on their spouse. And you found out cause you randomly saw them out somewhere.

Would you tell their spouse? Or would you keep it to yourself and go about your day/life.

You know now that I am older and have delt with friendship fallouts...I honestly wouldn't tell. Because I don't want to be in the middle of someone else's drama. And as the messenger, it seems you always get pulled into the drama and then get dumped as a friend.