A cybersecurity startup called Cathedral used AI agents to breach Anthropic’s internal business systems in under 12 hours. The researchers accessed meeting transcripts, employee salary data, and internal Slack discussions about advanced AI models. Anthropic has since disabled the affected systems and confirmed the scope of the breach.
The attack targeted third-party software that Anthropic uses for administrative and sales work. Importantly, the researchers did not break Claude itself or exploit Anthropic’s own code. In fact, Cathedral spent several days trying to crack Anthropic’s software directly. Then it shifted to the easier vendor applications.
Cathedral conducted the breach under Anthropic’s bug bounty program. Media reports and assessments describe it as an authorized security test rather than a criminal attack. However, Anthropic has accused Cathedral of overstating the national security implications. The company also said Cathedral did not fully disclose all its activity inside the systems.
AI agents identified potential access routes in under 12 hours, according to Cathedral’s draft report. The agents reportedly scanned systems, tested paths, and reviewed results with far less human waiting time. However, humans still set the scope and controlled the disclosure process.
Anthropic says the researchers accessed a limited group of sales, HR, and IT systems. These held business contact information for some customers and partners, plus basic user account records. Importantly, Claude customer prompts, model responses, source code, and model weights stayed untouched.
Anthropic’s monitoring flagged some of Cathedral’s actions before the startup reported them. As a result, the company shut off access the same day. It also disabled the affected business software until vendors confirmed fixes were ready.
Cathedral itself has an interesting background. Specifically, its four co-founders are former staffers from the Department of Government Efficiency (DOGE). Co-founder Gavin Kliger previously served as the Pentagon’s chief data officer. In July 2026, Cathedral raised $160M at a $1.4B valuation from Andreessen Horowitz and Sequoia Capital.
Three federal agencies have already contracted with Cathedral. According to a senior Trump administration official, the government is working with the startup on hostile AI scenarios.
