Polymarket Halts Trading After Third-Party Security Breach Causes User Losses

Polymarket confirmed that a security incident involving one of its external service providers led to unauthorized withdrawals from users’ accounts.

Prediction market platform Polymarket announced a temporary trading suspension after discovering that a third-party provider had been compromised, impacting users on its international platform.

The company disclosed the incident on Thursday following reports from users on X (formerly Twitter) who noticed that funds had been removed from their accounts without authorization. CoinDesk independently verified that users holding balances on Polymarket’s international venue had experienced account losses.

In an update published on its status page, Polymarket said it had identified and resolved the problem affecting its international platform. The company also confirmed that the compromised third-party provider had been referred to the appropriate law enforcement authorities.

Polymarket stated that affected users would receive compensation for their losses. However, trading remained suspended while the platform addressed the incident.

This marks the second third-party security breach involving Polymarket users in recent months. In June, the company disclosed that another external vendor had suffered a breach affecting its website’s front-end infrastructure. That incident resulted in approximately $3 million in stolen user funds.

Data from DeFiLlama indicates that Thursday’s incident resulted in estimated losses of around $2.7 million, slightly below the amount stolen in the previous breach.

Updates: The report was updated on October 29, 2026, at 19:33 UTC to include additional details and again at 19:39 UTC to revise the estimated losses.