Trading has resumed on Polymarket’s flagship international platform after a hack that drained money from the wallets of some traders.

A third-party vendor based in the United Kingdom was breached, not the prediction market’s website itself. Law enforcement in the UK have been notified of the incident, the company said. Trading was initially paused while the company investigated for several hours.

On X, prominent traders complained that they had lost money; blockchain analytics firm Bubblemaps reported that around 700 users appeared to have been affected, with approximately $2.7 million stolen. Polymarket declined to comment when WIRED asked how many traders were impacted by the breach and how much money was lost, but the company said it will refund impacted traders.

The hack did not impact users on Polymarket US, the company’s newer platform for people within the United States. Polymarket runs two separate prediction markets; Polymarket US operates as a federally regulated financial exchange within the country, while the flagship Polymarket is a cryptocurrency-based platform that is banned in the United States and a number of other countries.

This is not the first time that Polymarket traders have experienced security woes. In June 2026, Polymarket experienced another breach, which resulted in over $2 million in losses for impacted traders.

The company has been a lightning rod for controversy since its 2020 launch. In the past few years, it has been the center of several high-profile alleged insider trading incidents resulting in 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. In both cases, the suspects have pleaded not guilty.

Polymarket recently raised $1 billion in August 2026, with a fundraising round led by 1789 Capital, the venture capital firm where Donald Trump Jr. is a partner. It is now valued at $21 billion.