The company says an unnamed third-party provider was compromised. Trading has resumed, and Polymarket says affected traders will be made whole. Predictions markets platform Polymarket was forced to halt trading on its international platform Thursday for nearly an hour because of what it said was a third-party compromise. Polymarket has not put a number on Thursday's losses, which outside estimates based on blockchain data put at about $2.2 million to $2.65 million.