Polymarket restarted trading on its international platform on Thursday afternoon after a breach at a third-party provider let attackers drain funds from traders' accounts, with blockchain analytics firm Bubblemaps estimating that roughly 700 users lost about $2.7 million.
The prediction market put the platform into cancel-only mode while it investigated, then said a fix was in place. "A fix is out and we're keeping an eye on it. Trading will resume at approximately 3pm ET," the company's Polymarket Status account posted on X.
Polymarket said the compromised party was a vendor, not its own website, and that it had referred the matter to law enforcement. WIRED reported that the vendor is based in the United Kingdom. The company told users that anyone affected would be made whole, and Forbes reported that it described the remedy as full reimbursement.
Polymarket declined to say how many traders were hit or how much money was taken, according to WIRED. The Bubblemaps figure came from on-chain analysis the firm published on X, and the company has not confirmed it.
Traders first raised the alarm on social media, saying positions had been sold without their consent and balances emptied. Cointelegraph reported that the disruption was logged as a major outage of Polymarket's predictions trading API before all systems were listed as operational again at 7:05pm UTC.
The incident did not touch Polymarket US, the separately run, federally regulated exchange for American customers. The flagship platform is a crypto-based venue that is barred in the United States and several other countries.
It is the second security failure at Polymarket this year. A breach in June 2026 cost affected traders more than $2 million, WIRED reported. The company raised $1 billion in August 2026 in a round led by 1789 Capital, the venture firm where Donald Trump Jr. is a partner, valuing it at $21 billion.
Polymarket has also drawn scrutiny over alleged insider trading on its markets. A US special forces soldier accused of betting on the capture of Venezuela's former leader and a Google employee accused of using confidential information have both pleaded not guilty.