Winsage
June 24, 2026
A malware campaign targets Windows systems through a malicious npm package named postcss-minify-selector-parser, which mimics the legitimate postcss-selector-parser. This counterfeit package installs a Remote Access Trojan (RAT) on developer machines, beginning with a multi-stage attack triggered by the installation of the package. The RAT can steal credentials, execute shell commands, and communicate with a remote attacker. Security researchers at JFrog identified this threat and reported it on June 22, 2026, noting that two additional related packages, postcss-minify-selector and aes-decode-runner-pro, are linked to the same publisher and remain live on the npm registry.
The RAT employs encrypted HTTP communication with a command-and-control (C2) server and ensures persistence by creating a registry key under the Windows Run key. It has capabilities for remote shell execution, file uploads and downloads, and can steal saved login data from Google Chrome using Windows decryption APIs. The malware is designed for organized batch exfiltration of stolen data.
Indicators of compromise include specific IP addresses, domains, file paths, and SHA-256 hashes associated with the malware components. JFrog advises users to remove the malicious packages, inspect their dependency trees, and treat any stored credentials as compromised.
