Key facts
- Polymarket halted trading and switched to cancel-only mode due to a security incident.
- Users reported unauthorized asset withdrawals from their accounts.
- A suspected attacker's wallet holds approximately $2.65 million in POL.
- Polymarket stated impacted users will be made whole and referred the incident to law enforcement.
Polymarket, a decentralized prediction market platform, suspended trading actions and entered cancel-only mode on Thursday, October 29, 2026, following a security incident. Users reported unauthorized withdrawals of funds, with one trader claiming losses of $800,000 and another $600,000. The platform attributed the issue to a compromise of a third-party provider, stating that impacted users would be reimbursed. MetaMask stated that its users were unaffected as they do not use Polymarket's front end or SDKs.