MAL-2026-13344 Malicious code in ezfnfix (npm)

On Windows, npm install ezfnfix automatically executes a bundled Windows PE binary via a postinstall hook. package.json declares scripts.postinstall = "node postinstall.js", and postinstall.js enumerates bin/*.exe and runs the first entry with execFileSync. The shipped bin/ezfn.exe is a ~114 KB VB.NET executable whose metadata contains identifiers consistent with a remote-access trojan and infostealer: Telegram bot exfiltration primitives (SendBot, ChatID), socket C2 (ClientSocket, ConnectServer, ActivatePong), a spreading routine (Spread), AV/Defender-exclusion logic (Exclusion), webcam access (avicap32.dll), WMI-based host enumeration (ManagementObjectSearcher, get_UserName, get_MachineName, get_OSFullName, get_TotalPhysicalMemory), registry persistence handles (RegistryKey, CurrentUser), symmetric cryptography primitives, and WebClient/DownloadString network fetch. The binary ships with no source, no build step, no hash or signature verification, and no purpose consistent with the package name. Installing on Windows results in immediate execution of the RAT against the installer's host, exfiltrating identity and system information via Telegram/socket channels and providing persistent remote access.