Prediction market platform Polymarket resumed trading Thursday after a security breach involving a third-party service provider prompted reports of unauthorized withdrawals from user accounts and temporarily disrupted its international exchange. The company said it had identified and corrected the issue, referred the incident to law enforcement in the United Kingdom and committed to reimbursing affected traders.

Polymarket initially restricted its international exchange to cancel-only mode at 2:05 p.m. Eastern, temporarily preventing new trading activity while the company investigated. At 2:37 p.m., it confirmed that a third-party provider had been compromised and that the affected issue had been fixed. Trading resumed approximately an hour after the initial suspension, with the incident officially marked resolved at 3:05 p.m.

Reuters, citing a person familiar with the matter, identified the provider as DebugBear, a company specializing in website performance monitoring and debugging. DebugBear separately acknowledged a security incident and advised customers using its Real User Monitoring product to remove embedded monitoring code from their websites. Reports of unauthorized transactions raised concerns about the security of users' funds on the platform.

The number of affected accounts and the total financial losses have not been officially established. Polymarket said impacted traders would be fully reimbursed. The confirmed disruption involved Polymarket's international platform, while its separately operated U.S. exchange was not reported to have been affected.