Saying their early investor was the CIA isn’t exactly controversial. It’s cited in almost every article about the company. When something is that widely known, it’s usually not cited.

But since you asked, here is an old article about it: https://www.bizjournals.com/sanjose/news/2014/09/15/cia-back...

Title: CIA-backed Palantir adds $50M to its war chest

“Palantir's backers include the CIA's In-Q-Tel venture fund and Thiel's Founders Fund. Its customers include government intelligence agencies such as the National Security Agency.”

Google In-Q-Tel and Palantir and you’ll find 100 other articles about it.