Prediction market Polymarket lost more than $573,000 in a private key breach on Friday, hours after South Korea's media regulator opened a probe into whether the platform amounts to illegal gambling.
Polymarket Hack Drains Internal Wallet
The attack surfaced on Friday when on-chain investigator ZachXBT flagged suspicious outflows tied to Polymarket on the Polygon network. Analytics firm Bubblemaps then warned users to pause activity as the attacker steadily pulled roughly 5,000 POL tokens every 30 seconds.
The stolen assets moved across 16 wallets before reaching crypto exchanges.
Polymarket's developer account said trading infrastructure and customer balances were untouched. Engineering staffer Josh Stevens described the cause as a six-year-old private key linked to an internal top-up wallet, not a contract failure. He later confirmed that responders froze $164,000 of the $573,200 drained.
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South Korea Probe Adds Pressure
The breach landed as Polymarket faced fresh scrutiny abroad. South Korea's Korea Communications Standards Commission has opened a formal review into whether the prediction market hosts illegal gambling content under national law.
A commission official said the review followed a recent complaint against the platform.
Analysts note the timing matters because the compromised wallet sat near Polymarket's UMA CTF Adapter, the layer that settles prediction markets through an oracle. Stevens stressed that the administrative reward wallet operates separately from that resolution machinery, which limited the damage.
Researchers say the adapter is custom code that sits outside the audited core protocol, a recurring weak point for prediction markets. South Korea could move to block access, mirroring steps already taken by France, Germany and Italy.
Regulatory Crackdown Widens
Polymarket has spent 2026 absorbing enforcement actions on several fronts. The Korean inquiry follows earlier shutdown orders in Portugal and Hungary, civil action in Nevada, and cease-and-desist notices from Tennessee.
The platform secured U.S. approval from the Commodity Futures Trading Commission in late 2025, yet state regulators have continued pressing their own claims. That tension has left Polymarket expanding and contracting at once, banned in dozens of jurisdictions while courting fresh capital. The company was in talks in Apr. 2026 to raise about $400 million at a roughly $15 billion valuation.
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