MAL-2026-17317 Malicious code in booking-tasks (npm)

The package's package.json declares a postinstall hook wscript.exe 4444.vbs that fires automatically on npm install. The bundled 4444.vbs contains hand-rolled AES-128 (with XOR-masked forward/inverse S-boxes), a ChaCha20-IETF stream, XOR-masked SHA-256 round constants, a Base64 decoder via MSXML DOM, and a chunked Base64 ciphertext blob (ArtifactBundleHX, ~665 chunks). At install time the VBScript decrypts these chunks into a PowerShell loader, writes it to %TEMP%\pf<rand>.dat, and hands it to powershell.exe for process hollowing, giving the publisher arbitrary code execution on the installer's Windows host. The shipped library surface (src/index.js) is a small Zod-validated checkEligibility() function that never references 4444.vbs, and readme.md states 'No network requests. No personal data storage. No installation scripts.' — a direct contradiction of the declared postinstall hook, indicating the source module is a decoy for the dropper. The multi-primitive crypto and chunked-Base64 encoding of the payload serve only to hide executable content from static inspection.