Executive Summary
OX Security found npm package mouse5212-super-formatter uploading files from /mnt/user-data, a directory Claude uses for uploads and outputs.
What Happened
Cybersecurity researchers have discovered a new malicious package on the npm registry that comes with information stealing capabilities. According to OX Security, the package, named "mouse5212-super-formatter," is designed to upload files from "/mnt/user-data," a dedicated directory used by Anthropic's Claude artificial intelligence (AI) tool to handle uploads and outputs in the background. The
Affected Products
- npm
- Anthropic Claude
Vulnerability / Attack Technique
Malicious package stealing AI tool files
Technical Mechanism
Targets an AI tool's working directory.
AI Security Category
LLM02:2025 Sensitive Information Disclosure
Relevant Frameworks
RealGround Analysis
AI tool workspaces hold sensitive uploads. RealGround analysis: packages installed in AI sandboxes can read them.
Recommended Controls
- Limit packages installed in AI tool environments
Related RealGround Service
AI Agent SBOM and LLM Mapping · or start with the free AI Agent Security Scanner.
Sources
thehackernews.com: https://thehackernews.com/2026/05/malicious-npm-package-stole-files-from.html
Summary and analysis written by RealGround from the source above; last updated 2026-10-18.