Anthropic notified South Korea's Personal Information Protection Commission on October 31 that data from approximately 100 enterprise Claude accounts in South Korea had been leaked. The regulator is currently in a preliminary review stage and has not formally opened an investigation. The breach is linked to security firm Cathedral, which exploited a vulnerability in third-party business software to gain unauthorized access to Anthropic's internal systems. Exposed information includes account and organization identifiers, names, email addresses, and subscription plans. Anthropic employee Lydia Hallie confirmed on November 8 that prompts, outputs, and payment data were not accessed. The company severed affected systems on the day of discovery and coordinated with the vendor to patch the vulnerability.