A Polymarket security breach prompted a trading halt on October 29, 2026, after a compromised third-party provider left users on its international platform with drained accounts. DeFi Llama estimated losses at about $2.7 million , marking the second third-party breach to cost Polymarket users funds in recent months.
Users reported unauthorized withdrawals on X before Polymarket disclosed the incident on Thursday. The losses affected accounts holding balances on its international venue .
Polymarket said it had resolved the issue and referred the incident to law enforcement. “We have identified and fixed the issue impacting our international platform,” it said in a statement on its status page.
The statement identified a compromised outside provider as the source of the breach. Despite the trading suspension, Polymarket promised to make affected users whole .
Polymarket security breach follows June user losses
The latest security breach at Polymarket follows a separate third-party vendor compromise in June that resulted in approximately $3 million being stolen from users. Polymarket reported that the earlier incident affected its front end.
Both incidents involved outside providers and losses of user funds. DeFi Llama’s estimate for Thursday’s breach puts the financial damage below the approximately $3 million taken in June.
For the October incident, Polymarket’s response included a trading suspension, a fix for the issue, a law-enforcement referral and a commitment to compensate users for their losses.
Article produced with the assistance of artificial intelligence and reviewed by the editorial team.
