Polymarket Announces $3.9 Million Refunds After Third-Party Security Breach
Polymarket has announced a $3.9 million reimbursement plan following a cybersecurity attack that compromised user wallets on October 29, 2026. The prediction market platform confirmed that hackers exploited a third-party monitoring script to execute unauthorized transactions and transfer cryptocurrency from affected accounts.
In an October 30 security update, Polymarket said the compensation package includes $2.7 million in attack-related losses and another $1.2 million for trading disruptions. The company reported that 95% of affected wallets had already received full refunds.
Compromised Script Exposes User Wallets
The attack originated from a compromised performance-monitoring script supplied by an external technology provider. Attackers replaced the legitimate script with malicious code designed to exploit active trading sessions on Polymarket’s international platform.
The malicious script allowed unauthorized transactions while users remained logged into their accounts. Hackers used those sessions to sell trading positions and transfer funds from cryptocurrency wallets without the account holders’ authorization.
Reuters identified the affected provider as DebugBear, a website performance monitoring company. The vendor acknowledged a security incident and advised customers to remove its monitoring code while investigating the compromise.
Polymarket temporarily suspended trading and transaction processing after detecting suspicious activity. The platform subsequently removed the malicious script, cleared website caches, and reset active login sessions before restoring normal operations.
Refund Plan Covers Trading Disruptions
Polymarket’s reimbursement program extends beyond funds directly stolen during the attack. The company also committed to compensating traders who experienced financial losses because of the temporary trading suspension.
The additional $1.2 million covers qualifying losses involving positions affected by the trading interruption. These include positions that lost value when markets closed during the pause and certain transactions completed after trading resumed.
Polymarket said eligible users would receive compensation automatically based on blockchain records and trading activity. Customers who believe their reimbursements are incorrect can request an additional review.
Security Measures Target Third-Party Risks
The incident highlights security vulnerabilities associated with external software integrated into cryptocurrency trading platforms. Even when core blockchain infrastructure remains operational, compromised website components can expose users to substantial financial losses.
Polymarket said it is strengthening its security controls through stricter script verification, additional monitoring, and improved restrictions on third-party code. The company has also referred the incident to law enforcement and continues investigating the attackers.
The $3.9 million compensation commitment represents a significant financial response to the breach. However, the incident underscores the importance of protecting active trading sessions as prediction markets attract broader participation.
