The trades underscore fears that prediction markets can be used to profit from classified intelligence.

A mysterious online bettor made more than $400,000 on Polymarket, a website that lets people wager cryptocurrency on the odds of real-world events occurring, by correctly predicting the U.S. would invade Venezuela and topple President Nicolás Maduro.

The bets, which are viewable on Polymarket’s website, have prompted fresh concern that the rise of Polymarket and other platforms like it can allow insiders privy to confidential or even classified information to easily use their knowledge to profit.

In the early hours of Saturday, the U.S. military conducted a special operation to capture Maduro and his wife and bring them to the U.S. to face narco-terrorism charges.