ChainThink report, March 27, 2026: According to monitoring by 1M AI News, Anthropic inadvertently exposed unpublished blog drafts and other assets related to the upcoming Claude Mythos model due to a misconfiguration in its content management system, storing them in an unencrypted, publicly searchable database.

Claude Mythos is a new model currently under testing by Anthropic, positioned above the existing Opus series. Anthropic confirms it represents a leap in capability, marking the most powerful model built to date. The leaked drafts indicate significant performance improvements over Claude Opus 4.6 across software programming, academic reasoning, and cybersecurity benchmarks, with cybersecurity capabilities far surpassing all existing AI models. The draft also references the codename "Capybara," which points to the same underlying model as Mythos.

The breach also involved nearly 3,000 unpublished assets, including images, PDFs, and confidential details of the upcoming European CEO Executive Summit in the UK, where CEO Dario Amodei is scheduled to attend. The incident was independently discovered by Alexandre Pauwels, a cybersecurity researcher at the University of Cambridge, and Roy Paz, Senior AI Security Researcher at LayerX Security. Anthropic stated that due to the model’s exceptional capabilities, it will follow a cautious release strategy—initially limited to a small group of early customers and focused on cybersecurity defense scenarios—and will not be publicly accessible in the near term, citing extremely high operational costs.