After 10 years in the publicity-savvy Kardashian family, Kourtney’s ex Scott Disick has learned how to grab a headline. So when Rob Kardashian’s former fiancée, Blac Chyna — who’s suing Rob, his sister Kim, and their mother, Kris Jenner — threw a first birthday party for daughter Dream at her LA home in mid-November, Scott made sure to show up for the mermaid-themed bash. “The Kardashians hate Chyna with a passion,” notes a source. “Kris [Jenner] and Kourtney went ballistic when they found out and accused Scott of betraying them.”

His next move could start a war. Scott, 34, is threatening to write a tell-all about the entire Kardashian clan, sources tell Life & Style. And one insider says a juicy, detail-packed tome could go for $10 million. “Scott’s threatened to write a tell-all book before, but Kourtney has always talked him out of it,” notes the source. Though he’s moved on from Kourtney with 19-year-old model Sofia Richie, the insider says Scott wants revenge on the family for capitalizing on his addiction issues and personal demons for ratings on Keeping Up With the Kardashians for years. Adds another source: “Now that he’s not as involved with her or the family, a huge payday from a publisher sounds better than ever.”

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Kourtney is particularly panicked. During the exes’ nearly decade-long on/off romance, Kourtney had her fair share of flings, including a whirlwind romance with Justin Bieber in 2015. “Scott will reveal details about her relationship with Justin and other secret boy toys,” says the source.

Expect a few titillating passages on Kim, 37, and her husband, Kanye West, too. “Kourtney told
Scott about Kim and Kanye’s volatile marriage,” says the source, adding that he also knows all about Kim’s outrageous diva demands and “how she and Kanye lead separate lives.”

“Scott knows so many personal details about the Kardashians,” says a friend. “Everything from their plastic surgery secrets to how much Kris really drinks.” A friend adds that Scott has shocking new details to spill about Kanye, 40, who was hospitalized after a breakdown in 2016. “Scott knows [the truth] about Kanye’s mental health.”

Family matriarch Kris, 62, may soon regret ever opening up to Scott. “Kris has shared a lot of the family history with Scott, including her wild life and secret affairs,” says the source.

Bracing for the worst, the Kardashians have begun to do damage control. Kourtney and her family members “told all the nannies and [friends] not to say much when Scott is around,” says the Kourtney friend. “They want Scott to sign a nondisclosure agreement but they know things could turn even more ugly if they broach that subject with him. So for now they’re just hoping that the secrets stay with him,” says the source. But t,.hat’s not likely. “Scott holds a grudge.”