Polymarket resolves security issue after third-party breach

The prediction market says a compromised vendor caused the problem on its international platform, and it has referred the matter to law enforcement Polymarket says it has fixed a security issue on its international platform. The cause was not its own code but a third-party provider that got compromised. The prediction market has also referred the matter to law enforcement. That step turns an engineering cleanup into a potential criminal case. The research describes this as a supply-chain attack. Malicious code was reportedly injected into the platform’s frontend on or around June 25, 2026.