To Mind my own business or not

[Currant Bun]

Hi all. I'd appreciate some thoughts on this little problem I have.

I've accidently discovered that a female friend of mine at work is having an affair with one of her husband's mates. She never has a bad word to say about her husband, so it came as a massive surprise to find out that she was seeing someone else.

I care a lot for my friend and would hate to see everything go wrong if her husband found out about her affair, so I'm tempted to say something to her or let this other bloke know that people know what's going on. However I'm concerned that she might not appreciate me getting involved. Am I better to let her get on with her own life and deal with the consequences herself, or as a friend who cares, should I say something?

I'd appreciate any views or tales of experience. Thanks in advance.