Vulnerability MAL-2026-17449

This package is a fork of the Baileys WhatsApp Web library (npm) and belongs to the "PhantomSub" family described by OX Security in September 2026: the publisher injected code that, without the installer asking, uses the installer's own authenticated WhatsApp session to subscribe that account to WhatsApp Channels (newsletters) the publisher chose, by sending the WhatsApp w:mex FOLLOW query (query_id 7871414976211147) for each target channel JID.

package/lib/Socket/newsletter.js lines 62-103 define AUTO_FOLLOW_JIDS, eight base64 strings decoded with Buffer.from(..., "base64"), and when the connection opens (line 102) schedule a FOLLOW query for each, 90 seconds apart (cited line 90: await newsletterWMexQuery(jid, QueryIds.FOLLOW);). Decoded JIDs: 120363430764800148@newsletter, 120363400505489366@newsletter, 120363427794786523@newsletter, 120363428149518339@newsletter, 120363411665168068@newsletter, 120363410421978309@newsletter, 120363426605069018@newsletter and 120363425633124233@newsletter. There is no opt-out and the behavior is not documented.

Line numbers refer to version 1.0.0.

Static review of the published tarball(s) found no code that sends WhatsApp credentials or session keys off-host, no install-time payload (the only install hook is Baileys' stock Node.js version check in engine-requirements.js), and no persistence; the payload runs when an application creates a WhatsApp socket with the library. The harm is the covert use of the victim's account to inflate the publisher's channel subscribers.

SHA-256 of the published npm tarball(s): 1.0.0: 9451d13f06ff94c6d627f7ba7d8a7ad7f73a6cfbb856c7f4c2e29c3b187484bb.