Malicious npm Packages Pose as PostCSS Tools to Deliver Windows RAT

Summary

Cybersecurity researchers have identified several malicious npm packages posing as PostCSS tools, which are used to deploy a Windows-based remote access trojan (RAT). These packages, including 'aes-decode-runner-pro', 'postcss-minify-selector', and 'postcss-minify-selector-parser', were published by an npm user named 'abdrizak' and remain available for download. The attack chain involves a JavaScript dropper, a PowerShell script for downloading a ZIP archive, and a Visual Basic script to set up a Python environment for the RAT's core logic.

Full text

Malicious npm Packages Pose as PostCSS Tools to Deliver Windows RAT Ravie LakshmananJun 23, 2026Supply Chain Attack / Developer Security Cybersecurity researchers have discovered a set of malicious npm packages that are designed to deliver a Windows-based remote access trojan (RAT). The list of identified packages, is below - aes-decode-runner-pro (145 downloads) postcss-minify-selector (256 downloads) postcss-minify-selector-parser (615 downloads) All the packages were published over the past month by an npm user named "abdrizak" and continue to be available for download from npm as of writing. "Aes-decode-runner-pro and postcss-minify-selector-parser both present themselves as layered AES/custom-codec packages and depend on the legitimate postcss-selector-parser," JFrog said in an analysis. "Postcss-minify-selector presents itself as a PostCSS selector minifier and depends on postcss-minify-selector-parser." As for "postcss-minify-selector-parser," the name is a reference to "postcss-selector-parser," a widely used npm library with more than 127 million weekly downloads. Regardless of the package downloaded, the attack chain leads to the deployment of the same Windows malware. The packages come embedded with a JavaScript dropper that writes a PowerShell script ("settings.ps1") to disk and executes it. The PowerShell script then acts as a downloader for a next-stage payload retrieved from an external server ("nvidiadriver[.]net") using the "curl.exe." The retrieved payload is a ZIP archive, from which a Visual Basic Script ("update.vbs") file is extracted and run using "wscript.exe." Also bundled in the downloaded ZIP file is a Python runtime, a Python loader ("loader.py"), and a number of Python extension modules (*.pyd) compiled using Nuitka. Visual Basic is responsible for setting up the Python environment on the compromised host and launching the "loader.py" script, which then triggers the core logic of the malware. The RAT is equipped to gather host information, siphon credentials from Google Chrome, collect data from Chrome extensions, run shell commands, and download/upload files to and from a command-and-control (C2) server ("95.216.92[.]207:8080"). These features are realized through a set of Python native extension modules - config.pyd, which contains constants, command IDs, C2 URL, registry key names api.pyd, which handles HTTP C2 packet exchange audiodriver.pyd, which handles the main RAT orchestration loop command.pyd, which profiles the host, runs virtual machine (VM) checks, file transfer, and shell execution auto.pyd, which performs Chrome credential and extension theft, bypassing app-bound encryption (ABE) protections util.pyd, which acts as tar/gzip archive helpers "This case shows how a small parser-like package can hide a multi-stage Windows payload while appearing related to legitimate build tooling with massive weekly usage," JFrog said. "For defenders, the important lesson is to treat lookalike build dependencies as potential delivery mechanisms, not just harmless naming noise." The discovery coincides with three other campaigns targeting the npm and TypeScript ecosystem - A malicious package named "apintergrationpost" that delivers a full-featured Linux RAT dubbed MYRA, while claiming to be a Node.js integration client for authorized red team exercises. "It compiles a native C rootkit during install, establishes three independent persistence mechanisms, masquerades as a systemd service, supports fileless execution, and provides interactive shell access with live screen streaming," SafeDep said. A malicious package named "@withgoogle/stitch-sdk" that impersonates Google's Stitch AI design tool but comes with capabilities to steal developer credentials from eight sources (Claude Code, git config, ~/.git-credentials, SSH public keys, GitHub CLI, npm config, ~/.npmrc, and ~/.docker/config.json) and exfiltrates them to an attacker-controlled domain ("stitch-production[.]org/api/v1"). A cluster of five packages ("procwire," "routecraft," "endpointmap," "bytecraft," and "staticlayer") that delivers a dropper binary on Windows hosts from an external server and executes it during npm install. The "routecraft" package lists "procwire" as a dependency, while the latter lists "endpointmap" and "bytecraft" as dependencies. The last package, "staticlayer," is designed to run on the server side and deliver files to a client that presents the dropper's exact User-Agent. Users who have installed any of the above packages are advised to remove them with immediate effect, remove any artifacts created by them, and rotate credentials from impacted developer machines. The findings also coincide with a supply chain attack targeting the "gonex-AI/Understand-Anything" knowledge graph tool to push a malicious payload that "beacons one of three hardcoded C2 servers, exfiltrates a campaign marker, XOR-decrypts and evaluates a downloaded bot client, then independently resolves a second-stage command from a Tron blockchain address whose latest transaction encodes a BSC transaction hash carrying the active payload." The activity overlaps with a North Korean supply chain operation dubbed PolinRider, which has been observed injecting obfuscated JavaScript into legitimate developers' configuration files across nearly 2,000 compromised GitHub repositories to deliver a known malware downloader and stealer referred to as BeaverTail, which then paves the way for the InvisibleFerret backdoor. "This attack combines three things that individually are familiar but together open a detection gap: an elaborate fake PR description with fabricated test evidence, a diff that hides its payload in horizontal whitespace, and a two-stage C2 where the second stage uses public blockchain infrastructure as a write-once, read-anywhere relay," SafeDep said. Found this article interesting? Follow us on Google News, Twitter and LinkedIn to read more exclusive content we post. SHARE     Tweet Share Share Share SHARE  Credential Theft, Developer Security, GitHub, North Korea, NPM, powershell, Python, Remote Access Trojan, Supply Chain Attack, Windows ⚡ Top Stories This Week Chrome V8 Zero-Day CVE-2026-11645 Exploited in the Wild - Patch Now Researchers Build Self-Replicating AI Worm That Operates Entirely on Local, Open-Weight Models Microsoft Defender RoguePlanet Zero-Day Grants SYSTEM Access on Updated Windows Anthropic Releases Claude Fable 5, Its Most Powerful AI Yet, With Cyber Safeguards Microsoft Patches Record 206 Flaws, Including Three Zero-Days and Critical RCE Bugs Ivanti, Fortinet, and SAP Release Patches for Multiple Critical Vulnerabilities Cybersecurity Stars Awards 2026: Winners Announced Across 95 Categories ThreatsDay Bulletin: Worm Code Leaked, AI Agent Phished, Claude Code Patch + 28 New Stories New GreatXML Exploit Bypasses Windows BitLocker via Recovery Partition XML Files Agentjacking Attack Tricks AI Coding Agents Into Running Malicious Code China-Linked Hackers Backdoored Linux Login Software to Hide for Nearly a Decade Critical Splunk Enterprise Flaw Lets Attackers Run Code Without Authentication U.S. Orders Anthropic to Suspend Fable 5 and Mythos 5 Access for Foreign Nationals Over 400 Arch Linux AUR Packages Hijacked to Deploy Infostealer and eBPF Rootkit Palo Alto Warns of Active Exploitation of PAN-OS GlobalProtect VPN Flaw ⚡ Weekly Recap: Chrome 0-Day, UniFi Exploits, macOS Stealers, VPN Flaw and More ⭐ Featured Resources Get the 2026 Guide to Govern and Secure Enterprise AI Agents at Scale [Watch Demo] See Which Security Gaps Attackers Could Exploit First AI Can’t Stop Every Attack. 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Indicators of Compromise

• domain — nvidiadriver[.]net
• domain — stitch-production[.]org

Entities