Prediction markets platform Polymarket was forced to halt trading on its international platform for nearly an hour on Thursday due to what it said was a compromise of third-party software.
There have also been unconfirmed reports of users on Polymarket’s Discord channel saying their wallets had been emptied.
Although Polymarket did not confirm that users lost money, it stated in an X article that “anyone affected will be healed.”
“We will remedy this situation and will provide a full refund to all affected merchants,” the company said in a subsequent post on X.
Polymarket said the attack appeared to originate in the United Kingdom and that it had taken the matter to British law enforcement authorities.
The hackers gained access to the funds through DebugBear software, a web analytics and website performance tool, according to a person familiar with the details who was granted anonymity to address an evolving security situation.
DebugBear said on X that it was experiencing an “ongoing security incident” around 2 p.m. ET on Thursday.
Crypto news site The Block reported that some $2.65 million in cryptocurrencies were siphoned from Polymarket users’ wallets, citing data from blockchain analytics group Arkham.
A Polymarket representative declined to comment on that figure or the precise nature of the attack.
Polymarket said in its X post that it had identified and resolved an issue affecting its international platform, Polymarket.com.
“One of our third-party vendors was compromised and we have notified the appropriate law enforcement,” Polymarket said.
“Out of an abundance of caution, we have temporarily halted trading and are working to bring the platform back online,” he added.
Trading resumed at 3 p.m. ET after nearly an hour offline.
Polymarket’s US platform does not appear to be affected by this breach.
Compromising third-party vendors has become a common way for bad actors to gain access to major platforms and websites.
However, the success of these hackers in stealing Polymarket users’ money makes this a significant breach.
Polymarket was valued at $21 billion in September after a group of investors led by Donald Trump Jr. invested $1 billion in the platform.
The company currently processes approximately $200 million in business activities daily.
Polymarket, along with its rival Kalshi, has become the subject of an intense multi-million dollar battle between US states and the Trump administration over who should regulate the predictive market betting that takes place on the sites.
Platforms also continue to combat possible insider trading activity. Earlier Thursday, Bloomberg News reported that Polymarket was investigating reports of suspicious bets made in Israel’s closely watched elections.
The company is also investigating “dozens” of bets related to the U.S. midterm elections, according to Shana Bautista, the company’s head of global intelligence and investigations.
Earlier this month, Kalshi said she was investigating suspicious bets surrounding Trump’s choice for press secretary.
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