I found out a little while ago that someone I work with had an affair with the partner of a very close friend. (He also used to work in the same office).
The affair went on for about 18 months, ended a year ago, but they are still in contact. My friend found out 'cos he left his personal email account open; she went snooping and lo and behold - you can guess the rest.
Anyway, I don't have to work very closely with this woman, but we do have a few projects in common. I'm all for sweeping it under the carpet (I don't think it's any of my business what she or he got up to - my only concern is my friend), but things are a bit uncomfortable at work, as she knows I now know, and there have been a couple of awkward moments. You know the sort of thing, if both waiting for lifts, then she'll take the stairs.
Would you have a quiet word just to maintain normal working relations (I'm not even sure what I'd say), or just keep quiet and assume the awkward phase will blow over? (sorry for name change, but am bit paranoid about work).