Scott Disick felt "completely violated" after conversations with his therapist were leaked online.
The 37-year-old reality star checked into a rehab facility in Colorado earlier this year to work on his "past traumas", but checked out of the treatment centre a week later, after pictures of him were leaked online alongside the audio of his conversations with his therapist.
And in a sneak preview of an episode of 'Keeping Up with the Kardashians' that was filmed around the same time, Kourtney - with whom Scott has Mason, 10, Penelope, eight, and Reign, five - admitted her ex-boyfriend had "never felt more betrayed in his life" following the leak.
In the clip, Kourtney's sister Kim Kardashian West says: "I heard that Scott went to rehab by seeing it online. And it looks like someone at the facility leaked a photo of him. And I feel really bad for him."
To which Kourtney revealed: "They leaked his actual conversations, like, with the therapist.
"He's only been just him and the therapist. He said he's never been more betrayed in his life. And he is packing and he's definitely coming home but he's really upset, especially [because] he was going to work on himself and like, his traumas."
And in a confessional, 41-year-old Kourtney slammed those responsible for the leak.
She said: "I feel like whoever did leak this information should be really ashamed of themselves. Everyone deserves to deal with their past traumas in privacy. He was completely violated."
Back in May, Scott and his legal team announced they were seeking legal action against the treatment centre.
Scott's lawyer, Marty Singer, said in a statement: "In an effort to finally come to terms and deal with the pain that Scott has been silently suffering for many years due to the sudden death of his mother, followed by the death of his father 3 months later, Scott made the decision to check himself into a rehab facility last week to work on his past traumas. He did not check in for any alcohol or cocaine abuse.
"Shockingly as a result of the HIPAA violation of the facility and his violation of privacy, he has checked himself out and is immediately returning home. We are alarmed by this extreme invasion of privacy and plan to take immediate legal action."