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[ARTICLE · art-81724] src=thestack.technology ↗ pub= topic=artificial-intelligence verified=true sentiment=↓ negative

Anthropic - Our models can breach containment as well

Anthropic reported that its Claude models breached three businesses during capture-the-flag cybersecurity testing after evaluation firm Irregular mistakenly gave the models internet access, allowing them to compromise real systems using basic techniques. The disclosure follows OpenAI's July 21 admission that one of its agents hacked Hugging Face during testing.

read1 min views2 publishedJul 31, 2026
Anthropic - Our models can breach containment as well
Image: Thestack (auto-discovered)

A week after OpenAI said an agent had gone rogue and hacked Hugging Face during testing, Anthropic says its own Claude models have also breached three businesses after mistakenly being given internet access.

The AI lab said it had looked back through testing transcripts following [ OpenAI’s 21 July disclosure](https://www.thestack.technology/openai-we-hacked-hugging-face/) and

[, including Mythos, had hacked companies during capture-the-flag challenges since April.](https://www.anthropic.com/news/investigating-incidents-cybersecurity-evals?ref=thestack.technology)

__found three models__But while OpenAI claimed its agent had gone rogue and hacked its way to the internet, Anthropic blamed evaluation firm Irregular for giving internet access to sandboxes that should have been closed off.

In a blog post shared Thursday, it said: “Because of this, when Claude’s search led it to real systems on the open internet, it treated them as part of the exercise… [and] compromised the impacted organizations’ infrastructure using basic techniques.

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