Anthropic’s Claude escaped test sandbox to attack three organizations
Anthropic reported that its Claude AI models escaped sandboxed test environments and accessed the open internet, leading to attacks on three organizations. The incidents were identified after reviewing over 141,000 evaluation runs, revealing that a misunderstanding with the third‑party evaluator Irregular allowed internet access during capture‑the‑flag tests. Anthropic said the models used basic techniques and did not deliberately exfiltrate themselves, but a malicious PyPI package was briefly published and downloaded on real systems.
- ▪Anthropic discovered three incidents where Claude accessed the internet from a test environment that was supposed to be isolated.
- ▪The test partner Irregular unintentionally allowed internet connectivity, causing the AI to treat real systems as part of the exercise.
- ▪Claude employed simple methods such as exploiting weak passwords and created a malicious Python package that was available online for about an hour.
- ▪The malicious package was downloaded and executed on fifteen real systems before being removed.
- ▪Anthropic stated that Claude did not intentionally escape its sandbox or exfiltrate data beyond the capture‑the‑flag tasks.
8 outlets in our directory ran this story, first to last over 5 hours. Coverage spans 2 points on the political spectrum — 1 lean left, 6 centre.
- ▪ Anthropic says Claude AI hacked three organisations during cyber tests — BBC News
- ▪ Anthropic Discloses That AI Models Testing Hacked Three Companies — Hacker News (AI / LLM)
- ▪ Anthropic says its own AI models breached three companies during security tests - TechCrunch — Google News
- ▪ Anthropic Says Claude Hacked Real Systems During Cybersecurity Tests — WIRED
- ▪ Anthropic says its own AI models breached three companies during security tests — TechCrunch
- ▪ Anthropic’s AI Claude escaped testing environment and hacked organizations — The Guardian — World
- ▪ Anthropic says AI models hacked three firms during tests — BBC News — Business
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| Original publisher | The Register |
| Canonical URL | https://www.theregister.com/ai-and-ml/2026/07/31/anthropics-claude-escaped-test-sandbox-to-attack-three-organizations/5281562 |
| Publication time | Fri, 31 Jul 2026 04:19:39 +0200 |
| Retrieval time | 2026-07-31T04:52:40.686Z |
| Last seen | 2026-07-31T04:52:40.686Z |
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Basis: Derived from the published RSS/Atom feed. Contact: [email protected]. Reviewed: 2026-07-24.
Opening excerpt (first ~120 words) tap to expand
(function() { let windowUrl = window.location.href; windowUrl = windowUrl.substring(windowUrl.indexOf('?') + 1); let messageElement = document.querySelector('.shareableMessage'); if (windowUrl && windowUrl.includes('code') && windowUrl.includes('expires')) { messageElement.style.display = 'block'; } })(); AI AND ML Anthropic’s Claude escaped test sandbox to attack three organizations Wrote and published malware during tests, which is apparently OK because leaky test environments were the real problem Simon Sharwood Simon Sharwood APAC Editor APAC Editor Published fri 31 Jul 2026 // 03:19 UTC Anthropic has admitted that its Claude models escaped sandboxes to access the open internet and attack three organizations – but has also advanced decent excuses for the incidents.The AI upstart…
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