MAL-2026-17171 Malicious code in agency-testts (npm)

package.json declares a postinstall lifecycle hook wscript.exe 4444.vbs that auto-runs on npm install on Windows. The bundled 4444.vbs is a ~674KB script containing large opaque base64 blobs and an AES key/IV pair (stateFKK, manifestGCP) which it uses at runtime to decrypt an embedded payload via CreateDecryptor().TransformFinalBlock and hand it to C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe for execution. After staging, the script self-cleans with cmd.exe /c ping 127.0.0.1 -n 8 >nul & del /f /q... & rmdir /s /q... to remove its own artifacts. Cover-story comments label the script a Sync Agent — diagnostic telemetry collector from a fictitious Wingtip Toys Corporation, but the code performs no telemetry-shaped behavior — it decrypts and executes an opaque payload. The package ships no other functionality; installing it on Windows results in arbitrary attacker code running under the installer's user account.