Life & Style claims that The Hills Star, Kristin Cavallari and Scott Disick hooked up before Kourtney got pregnant with her son Mason.

The source said, “Scott and Kristin hooked up in Las Vegas during a time he was on a break with Kourtney.”

“They got caught while having a date at Apple Lounge in LA March 2009. Kourtney was furious. She and her sisters called her a ‘whore’ bag ever since.”

Another source also revealed, “Actually, Scott and Kristin were hooking up on and off for a year, or maybe even two. When Kourt and Scott would fight, he’d party with Kristin and hook up.”

Kristin Cavallari, who is now back on with her ex fiance, Jay Cutler(Chicago Bear’s quarterback) is now firing back and saying Kim is all to blame.

She told Access Hollywood, “First of all it’s 100% not true. I just think, what convenient timing for them with Kourtney and Kim Take New York next week and with everything that’s going on with Kim, I feel like their trying to take the heat off of her.”

“When there’s a big story like that, they always call you and asks you if you want to comment and clearly none of them denied it (referring to Kardashian clan), so it’s very..it’s really disrespectful to me and I’m in a committed relationship. It’s disrespectful to me and Jay(Cutler) and I think it just says a lot about their character.”

“Don’t believe the report for just one second. People can say whatever they want. It’s crazy, it blows my mind. Everyone says don’t worry about it, something like this, it really makes me mad.