[Anthropic Reports Claude Breach to South Korea, Involving Approximately 100 Corporate Accounts] According to Yonhap News Agency, the South Korean Personal Data Protection Commission stated today that Anthropic reported to the commission on October 31st that information from approximately 100 South Korean corporate Claude accounts had been leaked. The commission is currently in the preliminary review stage and has not yet formally launched an investigation. This leak is believed to be related to the security company Cathedral exploiting a vulnerability in third-party business software to gain unauthorized access to Anthropic's internal systems. The potentially exposed information includes account and organization identification numbers, names, and email addresses. Anthropic employee Lydia Hallie posted on the X platform on November 8th that Cathedral accessed account information such as names, email addresses, and subscription plans, but did not access prompts, output content, or payment information. The company shut down the affected systems and worked with the supplier to fix the vulnerability on the day it was discovered.