I think it is important to let THEM know you know and that you are not ok with it.
After that. Just remember IF your M can be saved your spouse will have a lot of guilt (righfully so) and each person you tell will be another hill they have to climb on the way back.
So
Think about what you are doing. And why.
Especially why.
You are fresh in this tragedy and the tendency is to act on emotion and anger.
IMO that only bites you in the a$$.
Don't do anything that has anger behind it.
It is not your job to teach life lessons to your spouse.
You can waste a lot of precious time gathering intel, strategizing, and exposing.
Would you rather she come back to you because she is ashamed or guilty
or
Because she realizes that she wants her M?
This is not a game. You want to save your M the path is to save yourself first.
This site is called DIVORCE BUSTING not AFFAIR BUSTING.
So I say again think of what you are doing and why.
And I say get to gettin' there.
My goal is to some day be the person my dog thinks I am