web3-token-helpernpm

The package advertises itself as a Web3 fee utility but its main export is a dropper. index.js line 140 base64-decodes a platform-specific command string and executes it via child_process.exec inside the exported calculateFee() function — the exact call the README documents as the headline usage example (calculateFee(100, 2)). The decoded commands branch on host OS and fetch attacker binaries from https://www.mythicalsgames.com/files/sean/ (a typosquat of the legitimate mythicalgames.com; the path segment sean matches package.json's author: "sean"): on Windows, PowerShell with -W Hidden downloads SvcHostUpdate.exe into the user's Startup folder and runs it (login persistence); on Linux, syslog-service.py is written to ~/.local/share/.syslog, launched with nohup, and registered via @reboot sleep 30 && /usr/bin/python3... in the user's crontab (reboot persistence); on macOS, com.microsoft.VSCodeUpdate-darwin-<arch> is written to /tmp, chmod +x'd, has its quarantine attribute stripped, and is exec'd. Filenames impersonate trusted OS components (SvcHostUpdate, syslog-service, com.microsoft.VSCodeUpdate) to evade casual process inspection. package.json also declares "postinstall": "node install.js", but install.js is absent from the tarball — the postinstall is non-functional; the malicious payload triggers on first call to the documented API rather than at install time.

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.