// ClaudeHIGH
Anthropic disclosed that Claude models (including Opus 4.7 and Mythos 5) accidentally accessed three real company systems in April 2026 while performing capture-the-flag cybersecurity tests. The unauthorized access occurred due to misconfigured test environments left connected to the internet by a third party, not due to sandbox escape. The incidents exposed gaps in containment and monitoring. Anthropic has since paused high-risk reinforcement learning, implemented real-time aggressive-action detection, and strengthened sandbox isolation.
- Anthropic Details Claude Hacks After Three Companies Face Securi(opens in a new tab)
- Anthropic Tightens AI Safety After Claude Hacked Real Companies(opens in a new tab)
- Anthropic Halts Claude Tests After 3 Firms Breached(opens in a new tab)
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