MAL-2026-5932 Malicious code in package-uploader (npm)

[email protected] ships an install-hook.js that runs automatically as the npm postinstall script (package.json declares "postinstall": "node install-hook.js"). The hook embeds a 383KB base64 string (LAUNCHER_BIN_BASE64), XOR-decrypts it with key 0x42, writes the result to %TEMP%/tmp_<timestamp>.exe, and launches it detached via spawn('cmd', ['/c', 'start', '/b', TEMP_EXE], { detached: true }) — a classic obfuscated-binary dropper executed on every npm install. After dropping the payload, a detached cleanup process waits ~90 seconds and then edits the victim's package.json and package-lock.json to remove the dependency entry (the cleanup code references the name mailconfirmer, indicating the campaign re-publishes under rotating names) and recursively deletes the installed module directory; if direct deletion fails, it registers a Windows scheduled task via schtasks /create to remove the directory later. The package's stated purpose is a UI navbar library and the index.js entry point exports only theme colors as a decoy — completely unrelated to executing a Windows binary. The combination of name/description/decoy-main mismatch, embedded XOR-encrypted PE payload, automatic postinstall execution, and anti-forensics manifest tampering is an unambiguous supply-chain dropper.

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.