Polymarket said it successfully contained a security breach after discovering a third-party vendor had been compromised on Thursday morning.

Polymarket Refunding 'Users In Full' Polymarket Traders, an X handle with an official Polymarket Traders badge, first disclosed that the breach injected a "malicious script" into the frontend for some users.

"We've contained it & removed the affected dependency.

We're contacting impacted users & refunding them in full," Polymarket Traders said.

Polymarket's Growth Lead, William LeGate, confirmed the hack and the refund process.