All spilled on a live TV show.
Appearing on American live TV show Watch What Happens Live on Thursday night, a caller asked fellow guest Jon Cryer, 49, whether it was awkward working with Kutcher on the set of Two and a Half Men given both men had been in a relationship with Moore.
Cryer dated Moore in the 1980s – when Kutcher was only seven years old – while Kutcher and Moore were married from 2005 to 2013. Kutcher is now engaged to actress Mila Kunis and the pair now have a daughter, Wyatt Isabelle.
"Yeah it was a little awkward I have to say," Cryer began to say, looking rather embarrassed.
But that's when Eastwood decided to drop this bombshell:
"If it makes you feel any better, he did sleep with one of my ex-girlfriends - but she was my current girlfriend at the time."
Say what now?
"Well, I think it was the catalyst that broke him and Demi up," Eastwood, 29, continued.
The Hollywood actor then went on to confirm his girlfriend at the time was one of the two girls involved in the San Diego scandal that US Weekly reported in 2011, where Kutcher allegedly was caught cheating with two girls in a hot tub on his and Moore's sixth wedding anniversary.
Eastwood said he and one of his friends had been dating the two girls.
But when asked if he was still angry with Kutcher over the incident, Scott's answer was surprising.
"No, not at all," he said.
Eastwood stars in romantic drama The Longest Ride - his first lead role in a movie - that was released in Australia on 9 April.
CLICK THROUGH the gallery for more photos of Demi and Ashton:
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