Polymarket froze trading on its international exchange on Thursday, October 29, 2026. The halt followed user reports of emptied accounts. One trader said attackers drained $800,000 from their account, and another reported a $600,000 loss.

Roughly 20 minutes later, Polymarket moved the exchange into cancel-only mode. Users could cancel open orders, but the platform rejected new trades. Polymarket also paused its relayer, the service that submits transactions for users. The company said it acted “out of an abundance of caution” while it investigated. Notably, the U.S. platform did not appear to suffer any impact,

Attackers did not break Polymarket’s smart contracts. Instead, they compromised a third-party provider, which Polymarket never named. 

Reported losses vary, and Polymarket has published no official total. Blockchain analysis put the figure between roughly $2.2 million and $2.7 million. Arkham reportedly linked about $2.65 million to the suspected attacker.