Forecasting market platform Polymarket disclosed that it halted all trading activity following a security compromise at an external vendor that impacted participants on its global marketplace.
Polymarket made the security incident public on Thursday after participants took to the social media platform X, previously known as Twitter, to report unauthorized withdrawals from their wallets. CoinDesk verified that accounts holding funds on Polymarket’s global site experienced unauthorized depletions.
An update posted on its status page stated, “We have identified and fixed the issue impacting our international platform. One of our third-party providers was compromised, and we have referred this to relevant law enforcement.”
The notification added that affected participants will be fully reimbursed, though market operations remain temporarily paused.
This marks the second occasion in recent months where Polymarket participants experienced financial losses stemming from an external service provider compromise. Back in June, Polymarket disclosed that a different external vendor suffered a breach that impacted the website’s user interface. That security event resulted in roughly $3 million being stolen from account holders.
Based on data from DeFi Llama, the scale of Thursday’s security breach fell just short of the prior incident, with monitored losses amounting to approximately $2.7 million.
UPDATE (Oct. 29, 2026, 19:33 UTC): Adds additional detail.
UPDATE (Oct. 29, 19:39 UTC): Updates loss estimate.
Originally published at https://www.coindesk.com/markets/2026/10/29/polymarket-suspends-trading-after-third-party-breach-leads-to-user-losses.
