Malicious code in monte-md-baileys (npm)

This package is part of a large family (100+ identified as of September 2026) of near-identical forks of the Baileys WhatsApp Web library that inject a covert channel-subscription action into the WhatsApp socket layer. On connect, the injected code issues an authenticated w:mex FOLLOW query (query_id 7871414976211147) against one or more attacker-chosen WhatsApp Channel/Newsletter JIDs, using the installer's own authenticated WhatsApp session -- silently subscribing the victim's account to channels it never asked to join.

The target JID(s) are hidden from casual source review via one of several obfuscation techniques observed across the family: a plain string literal, base64 encoding, base64+XOR, or a char-code array reconstructed at runtime. Some variants instead fetch a mutable, attacker-controlled remote JSON/JS list of target JIDs from GitHub or another host at runtime, letting the target list change after installation without a new npm publish. Every sample in the family shares the same underlying mechanism (a wrapped/patched socket-connect routine that fires the FOLLOW query some seconds after connect), even though the package name, JID value(s), and obfuscation/delivery method differ per fork.

The malicious action abuses the installer's own authenticated WhatsApp session to gain reach and subscribers for attacker-controlled channels; it does not exfiltrate credentials, establish persistence, or execute arbitrary remote code.

Affected package: monte-md-baileys (npm), version(s): 1.0.0.

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Source: amazon-inspector (489128924ea1bbd77b6e22bb1e8e2457b3e8c2c97caceb78d5fa3a029cde5104)

monte-md-baileys is a fork of the Baileys WhatsApp library. In lib/Socket/newsletter.js, a ws.on('open') handler silently issues a newsletter FOLLOW query for a hardcoded JID (120363407598531220@newsletter) one second after the WhatsApp WebSocket connects, causing the installer's authenticated WhatsApp session to auto-subscribe to the maintainer's channel. The behavior is not disclosed in the README and fires on every socket connect. No credential exfiltration, remote code execution, filesystem persistence, or environment scraping is observed; the covert side-effect is confined to a reach-padding action performed with the installer's WhatsApp identity.