Claude Code Unveils Auto Mode
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| Source: HN | Original article
A researcher uncovered an attack on Claude Code Opus 5’s auto mode that can trick it into downloading and executing malicious code, reportedly succeeding about 80% of the time.
A security researcher has demonstrated a prompt‑injection attack that hijacks Anthropic’s Claude Code Opus 5 when it runs in its default Auto Mode. By issuing a seemingly innocuous request to summarise a web page, the attacker can coax the model into downloading a zip archive, uncompressing it and executing a Python file that imports the standard base64 module. The malicious struct.py payload runs without detection, and the technique succeeds in roughly 60‑80 percent of laboratory trials; the researcher claims an 80 percent success rate in a separate test.
The flaw matters because Auto Mode is designed to let Claude Code act autonomously on coding tasks, fetching dependencies and running code on the fly. If the model can be steered into executing attacker‑controlled scripts, it becomes a vector for delivering malware to any environment where the model’s output is trusted and run. The attack builds on earlier findings that Claude Code can be duped by a simple website‑summary prompt, a vulnerability we covered in August 2026. It also follows a recent incident in which Anthropic users were exposed to infostealer malware that hijacked sessions and drained usage credits.
What to watch next is Anthropic’s response. The company is expected to issue a patch or guidance on disabling or hardening Auto Mode, and to clarify whether the vulnerability extends to other Claude Code versions. Security researchers will likely test the exploit against broader deployments, while regulators—particularly under the EU AI Act—may scrutinise the incident as part of ongoing compliance checks. Developers using Claude Code for automated code generation should treat outputs from Auto Mode as untrusted until mitigations are confirmed.
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