Polymarket has resumed trading on its flagship international prediction market after a breach at a third-party vendor allowed attackers to drain funds from some traders' wallets. The UK-based vendor was compromised, not Polymarket's own website, according to the company. Law enforcement in the United Kingdom have been notified. Trading was paused for several hours while Polymarket investigated.
The financial toll is still being tallied. Blockchain analytics firm Bubblemaps reported that roughly 700 users appear to have been affected, with about $2.7 million stolen. Prominent traders aired complaints about lost money on X. Polymarket declined to tell WIRED how many traders were impacted or how much money was lost, but said it will refund affected traders.
The hack did not touch Polymarket US, the company's newer platform for users inside the United States, which operates as a federally regulated financial exchange. The flagship Polymarket is a cryptocurrency-based platform that is banned in the United States and a number of other countries, leaving the two markets on separate infrastructure.
It is not the first security problem for Polymarket traders. In June 2026, the platform suffered another breach that cost impacted traders more than $2 million.
Polymarket has drawn controversy since its 2020 launch. In recent years it has been at the center of several high-profile alleged insider trading incidents that led to arrests. One case involved a special forces soldier accused of wagering on the capture of Venezuela's former leader. Another involved a Google employee who allegedly used confidential information to make millions. Both suspects have pleaded not guilty.
The company's business has grown alongside its notoriety. Polymarket raised $1 billion in August 2026 in a round led by 1789 Capital, the venture capital firm where Donald Trump Jr. is a partner. It is now valued at $21 billion.
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