Polymarket security breach halts trading as DeFi Llama estimates $2.7M loss

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.