A malicious JavaScript file was found in a third-party performance monitoring integration on Polymarket. The script was designed to access authenticated trading sessions, inspect user portfolios, and transfer cryptocurrency assets to attacker-controlled addresses. It operates by reading authentication data from local storage, navigating React components to find trading functions, and creating signed messages to move assets. Polymarket has removed the compromised third-party integration. The extent of victimization and total losses are currently unknown.