MAL-2026-17523 Malicious code in studiocode_tools (npm)

package.json declares a postinstall hook that runs wscript.exe 4444.vbs, auto-executing on npm install on Windows. The shipped 4444.vbs contains hand-rolled AES and ChaCha20 implementations with XOR-obfuscated S-boxes, SHA-256 round constants XORed with 0x5A5A5A5A, and hundreds of base64 ciphertext fragments (ArtifactBundleHX) that are reassembled and decrypted at runtime into a PowerShell loader. The script writes a payload file to %TEMP%\pfNNNNN.dat and invokes powershell.exe to perform process hollowing of the decrypted payload. The VBS carries cover-story branding as 'Verdant Signals Corp' / 'Device Telemetry Aggregator', and the README falsely states 'There are no installation scripts.' The multi-layer custom cryptography, false branding, and explicit README denial of install scripts are unambiguous indicators of hostile intent rather than legitimate functionality.