npm registry: Malicious ‘mouse5212-super-formatter’ package exfiltrated files from Claude users’ workspaces

A malicious npm package, mouse5212-super-formatter, posed as an archive-deployment sync utility but instead scanned the /mnt/user-data directory—where Claude stores uploaded files and work results—and uploaded every file it found to a remote GitHub repository under randomized, base64-encoded names. Researchers discovered the campaign after the package’s author accidentally hardcoded their own GitHub access token into the code, which let investigators observe roughly seven active exfiltration sessions before the package was removed. The package had been downloaded 676 times; researchers believe the malware itself was likely AI-generated.