Coding-agent memory files show no consistent security effect
Original title: Security Impact of Coding Agent's Memory Files
Malicious CLAUDE.md-style files shifted secure completions by -8 to +6 points, while disclosure behavior differed by agent.
The study treats project memory files that coding agents load as trusted guidance as an attack surface, including files changed through a pull request. For 12 CWE classes, researchers wrote qualified and forceful malicious files and tested Claude Code with Sonnet 5.5 and OpenCode with Qwen 3.8 27B and DeepSeek V4.1 Flash on 36 SecRepoBench tasks. Secure-completion rates changed by -8 to +6 percentage points, with no consistent pattern. Claude Code named the file in about two thirds of final messages, while OpenCode mostly mentioned it only in its reasoning trace; flagging the file as an attack still left vulnerable code.
Unconfirmed: The measured security effect was small and inconsistent across agents and file variants.
- Each of 12 CWE classes had qualified and forceful malicious memory files.
- The benchmark contained 36 SecRepoBench tasks, with and without the files.
- Secure-completion changes ranged from -8 to +6 percentage points.
- Claude Code named the file in about two thirds of final messages.
- The authors say larger studies are needed to quantify risk and design defenses.
- Products
- Claude CodeOpenCode
From the original article
1 min read at arxiv.orgCoding agents automatically load project memory files such as CLAUDE. md at the start of every session and treat them as trusted project guidance. Anyone who can change such a file, for example through a pull request, can therefore steer the agent without ever touching the developer's prompt.
By Thiago Santos de Moura · arxiv.org
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