A Fortune reporter found a data store attached to Anthropic's blog infrastructure sitting open to the public — no authentication, fully searchable — holding some 3,000 unpublished assets. Among them was a draft post announcing an unannounced model called Claude Mythos, which said the company regarded it as posing unprecedented cybersecurity risks; the drafts also used the name Capybara. Anthropic confirmed the model existed, calling it "a step change" in performance and "the most capable we've built to date," and said early access customers were trialling it. The cause was a configuration error in its content management system. A company that had built its position on safety had disclosed the existence of the model it considered most dangerous by its own mistake.