Cyberattacks | Software security

$2M+ Stolen From Polymarket in Supply Chain Attack Tied to Third-Party Vendor

Polymarket paused its international exchange after a hijacked monitoring script drained funds from logged-in traders. Reimbursement promised.

By Content Team

Nov 2, 2026

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Polymarket’s international platform halted trading on October 29, 2026, after a supply chain attack drained user funds. The company hasn’t disclosed losses, but the wallet believed to belong to the attacker held about $2.65 million, according to Arkham data. Researchers trace the malicious JavaScript to DebugBear, a UK firm that monitors website performance, through its real user monitoring script.

The code targeted logged-in users, selling positions or transferring tokens directly to an attacker-controlled wallet. DebugBear confirmed it was dealing with a security incident and told customers to remove its script. Polymarket, which hasn’t named the vendor, referred the breach to law enforcement and pledged to make every affected trader whole. Trading restarted roughly an hour later.

Polymarket’s US exchange appears to have been untouched. This is the company’s second third-party breach in months — a similar attack in June 2026 cost traders a reported $3 million.

Source: SecurityWeek

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