Polymarket, a prediction markets platform valued at $21 billion as of September 2026 [1], halted trading on its international platform on Thursday, October 29, 2026, for nearly an hour due to a compromise of a third-party vendor [1][2]. According to blockchain analysis group Arkham data cited by The Block, approximately $2.65 million in cryptocurrencies were siphoned from the platform [1]. Users reported unauthorized wallet drains on Polymarket's Discord channel and social media platforms [1][2]. Notably, Polymarket's U.S.-based platform was not affected by the breach [1].
In response to the incident, Polymarket identified and fixed the issue on its international platform (Polymarket.com) and referred the matter to relevant law enforcement [1]. The company stated it would "make this right and are fully reimbursing all affected traders" [1]. A Polymarket spokesperson clarified that the incident has been referred to U.K. law enforcement, as that is the country of operation for the third-party provider [2]. Trading resumed at 3 p.m. ET after the nearly one-hour halt [1].
The breach occurs amid heightened regulatory scrutiny of prediction markets. Polymarket and rival Kalshi are currently engaged in "an intense, multi-million-dollar battle between U.S. states and the Trump administration over who gets to regulate the prediction-market betting" on these platforms [1]. The incident also comes as Polymarket continues investigating suspicious trading activity, including "dozens" of suspicious bets related to the U.S. midterms and reports of suspicious bets made during Israel's elections [1]. The timing is particularly sensitive, as both Polymarket's international and U.S. exchanges are expected to experience heightened trading volumes during the U.S. midterm elections on November 3 [2].
CONCLUSION
Polymarket's security breach resulted in $2.65 million in cryptocurrency losses but was contained to the international platform, with the company committing to full reimbursement of affected users [1][2]. The incident underscores ongoing security vulnerabilities in decentralized finance platforms and adds complexity to the regulatory battles surrounding prediction markets ahead of the November 3 midterm elections [1][2].