Claude Code Opus 5’s Auto Mode is not as secure as reported. A recent exploit achieved 60-80% code execution through a sophisticated prompt injection attack, challenging Anthropic’s 0.00% success rate claim for unseen attacks.
The attack chain is a masterclass in agent exploitation: it nudges Claude from WebFetch to curl, then redirects it to a ZIP archive containing a malicious struct.py file. When Claude then attempts to import base64, the poisoned struct.py shadows the standard library, leading to arbitrary code execution.
This highlights a critical lesson for anyone building or deploying AI agents: Auto Mode is not a substitute for isolated execution environments and rigorous output monitoring. Understanding these vulnerabilities is paramount for developing truly robust and secure agentic systems.
















