Polymarket restored trading on its international platform after a security breach at a third-party vendor on October 29. The company has committed to fully reimbursing traders who lost money in the incident.
Blockchain analytics firm Bubblemaps estimates that approximately $2.7 million was stolen from roughly 700 users. Polymarket has not confirmed this figure.
Trading Pause and Response
Polymarket initially moved its exchange into cancel-only mode, allowing customers to withdraw existing orders while halting new trades. The company also paused its transaction submission service before identifying that one of its third-party providers had been compromised.
Trading remained suspended for several hours during the investigation. Polymarket later confirmed that trading had fully resumed on its international platform.
The compromised vendor is based in the United Kingdom, according to Polymarket. The company stated that its own website was not breached and that UK law enforcement has been notified.
Polymarket US, the company's federally regulated platform for American users, was not affected by the incident.
Attack Details
Bubblemaps traced stolen funds from hundreds of deposit wallets into addresses identified as belonging to the attacker. The firm tracked approximately $2.71 million moving through the primary route.
Researchers linked the attack to malicious code in a website performance-monitoring service. These tools are typically used to track website load times and performance. According to researchers, the malicious code accessed users' trading sessions and initiated actions that moved assets out of their accounts. The exact attack method remains under investigation.
The stolen funds were converted into POL, the native token of Polygon, and sent to multiple addresses, with additional transfers tracked to Ethereum.
Outstanding Questions
Polymarket has promised full refunds but has not provided a timeline or detailed claims process. The company has not disclosed how many traders were affected or specified which accounts qualify for reimbursement, how losses will be calculated, or when funds will be returned.
This is not Polymarket's first security incident. In June 2026, another breach resulted in more than $2 million in losses for affected traders.
