FULL STORY

Cathedral's Breach of Anthropic: From Authorized Test to Alleged Cover-up

An AI agent from Cathedral, a startup founded by ex-DOGE members, breached Anthropic's network in 12 hours during an authorized test. A developer later alleged Anthropic was downplaying a full Slack compromise.

2026-10-26 ~ 2026-10-28 · 2 episodes · 23 posts

Episode 1 · Ex-DOGE startup Cathedral breaches Anthropic's internal systems with AI agents in under 12 hours (2026-10-26, 18 posts)

According to a Washington Post exclusive, Cathedral, an AI cybersecurity startup founded by former DOGE members, revealed that during an authorized security test against Anthropic, its researchers used AI agents to find a path into Anthropic's sensitive internal systems in under 12 hours, obtaining a trove of sensitive documents — including Slack channels discussing the most sensitive model information, meeting notes, and employee data such as salaries and offer letters. Polymarket also posted the breaking news.

Confirmed

  • Cathedral informed Anthropic of the successful breach; the intrusion took place within the framework of an Anthropic-authorized security testing program
  • The penetration took under 12 hours and involved autonomous execution by AI agents
  • Accessible data included sensitive Slack channels, meeting notes, salaries, and offer letters

Unconfirmed

  • Technical details of the intrusion path: @AlexTensor reshared claims about how the breach was achieved, but the materials lack complete, reliable technical detail
  • Follow-up handling and remediation between Cathedral and Anthropic

Why it matters

  • The incident came shortly after an Anthropic whistleblower publicly criticized the company for keeping highly sensitive work on Slack, echoing that criticism
  • Anthropic, a company built around AI safety, was rapidly breached by AI agents — highlighting the asymmetric risks of AI-driven offense versus defense, and demonstrating the real-world power of AI agents in red-team security testing

Episode 2 · Unverified claims say Anthropic Slack was fully compromised by 'Cathedral' (2026-10-28, 5 posts)

Developer Will Depue claimed on X that Anthropic is downplaying a recent security incident, alleging the group 'Cathedral' obtained full admin access to its Slack workspace. Anthropic has not clarified the scope; claims remain unverified.