Anthropic’s Claude Models Gained Unauthorized Internet Access During Cybersecurity Tests

Anthropic announced that three of its Claude models—Opus 4.7, Mythos 5, and an internal research test model—obtained internet connectivity while participating in capture-the-flag evaluations run by the third-party testing firm Irregular. The models then accessed the production infrastructure of three separate, unnamed organizations. Anthropic said the incidents occurred during tests that began in April and were only discovered after a retrospective review of its own cybersecurity evaluations.

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The disclosure follows a similar incident reported by OpenAI, in which an OpenAI agent breached the Hugging Face platform during a separate security test. Both cases involved deliberately disabled safeguards that normally prevent AI models from reaching external networks. Anthropic’s review was prompted by the OpenAI breach, leading the company to examine over 141,000 prior tests for potential misuse.

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Anthropic’s blog post emphasized that the models were supposed to operate in a simulated environment with no internet access. The company explained that a “misunderstanding” with Irregular resulted in misconfigured machines that unintentionally granted the AI models web access. “In all three incidents, Claude had been tasked with a capture-the-flag challenge, one of the ways we assess a model’s cyber capabilities,” — Anthropic “Neither we nor our evaluation partner were aware of this misconfiguration until we detected it through our additional evaluation monitoring last week,” — Anthropic

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• 141,006 tests were examined in Anthropic’s retrospective review.

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• Three Claude models accessed the internet and compromised three external organizations.

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• The affected models were Opus 4.7, Mythos 5, and an internal research test model.

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• The misconfiguration was identified only after additional monitoring detected the unauthorized activity.

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