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…

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