Anthropic has suffered a security breach after a newly formed US-based AI startup successfully hacked its systems and accessed sensitive internal corporate data.

The startup, Cathedral, was founded this year by former staff members of the US Department of Government Efficiency (DOGE).

According to reports, the breach was carried out as part of a bug bounty program designed to encourage outside security researchers to uncover flaws. The intrusion exposed internal Slack messages, meeting transcripts, staff salaries and job offers.

Anthropic confirmed that Cathedral managed to reach a “limited set” of sales, HR, and IT systems, but assured customers that user conversations with the Claude AI model and the model’s underlying source code remained entirely uncompromised.

“Our monitoring flagged some of Cathedral’s activity before they reported it to us,” Anthropic said in an official statement. “We shut off their access the same day”.

While Cathedral claimed the breach was executed in less than 12 hours, Anthropic pushed back on that timeline, stating that the activity involved attempts spanning multiple days.

A spokesperson added that Cathedral’s actions went “substantially beyond” the intended scope of the bug bounty program by specifically targeting third-party applications.

Cybersecurity experts noted that the incident did not stem from an advanced, sophisticated AI exploit, but rather a basic hygiene failure involving third-party software.

Heath Mullins, Chief Evangelist at ExtraHop, highlighted the broader supply-chain implications for the tech sector: “When a handful of platforms sit at the centre of how a majority of businesses operate, a single compromise becomes a supply chain problem for everyone downstream”.

The security breach comes at a delicate time for Anthropic, arriving just hours after the lab filed paperwork for a massive initial public offering (IPO) on Nasdaq. The prospectus highlights the company’s grand ambitions to cure major diseases and reshape the global economy, while also warning investors of potential catastrophic risks.

Meanwhile, the breach has triggered sharp geopolitical anxiety: a senior Trump administration official warned, “If a bunch of kids who have just started a company can do this, then potentially the Chinese aren’t far behind”.

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