On October 29, 2026, Polymarket experienced a security vulnerability incident, which led to the suspension of trading. The cause was an intrusion into a third-party service provider, resulting in the transfer of funds from user accounts on its international platform. DeFi Llama estimated losses to be around 2.7 million US dollars. This is the second incident in recent months where third-party vulnerabilities have caused financial damage to Polymarket users.

Before Polymarket disclosed this matter on Thursday, some users had already reported unauthorized withdrawals on X. The losses affected accounts that held balances on their international trading platform.

Polymarket indicates that the issue has been resolved, and the matter has been referred to law enforcement for handling. The company stated on its status page, "We have identified and fixed the problem that affected the international platform."

The statement indicates that this vulnerability originated from an external service provider that was compromised. Although transactions were temporarily suspended, Polymarket has pledged to provide full compensation to the affected users.

Before the Polymarket security vulnerability occurred, there were also cases of user losses in June.

Both incidents involved external service providers and resulted in financial losses for users. DeFi Llama's estimation of the vulnerability on Thursday indicates that the financial loss was less than the approximately $3 million incurred in June.

Regarding the incident in October, Polymarket's response measures included suspending transactions, fixing the issues, handing over the case to law enforcement authorities, and committing to compensating users for their losses.

This article was generated with the assistance of artificial intelligence and has been reviewed by an editorial team.

Amelia Tomasicchio

As a digital marketing expert, Amelia began to enter the fintech field in 2014 after completing a thesis on Bitcoin technology. She had previously contributed to several international cryptocurrency-related magazines and served as the chief marketing officer for Eidoo. She is currently a co-founder of The Cryptonomist. She is also a marketing lecturer at Digital Coach in Milan and has published a book about NFT with an Italian publishing house Mondadori. Additionally, she has helped artists and businesses enter this field. As a consultant, Amelia has also participated in projects related to the metaverse, such as The Nemesis and OVER.