MAL-2026-17554 Malicious code in css-mpmdds-polyfill (npm)

The package presents itself as a CSS polyfill but ships thunderboltRegistry.js which runs an IIFE at module load. The IIFE acquires child_process via multiple fallbacks (require('child_process'), require('node:child_process'), and a synthesized Module constructor), executes shell commands to collect host identity (id, whoami, uname -a, ifconfig/ip addr, /etc/hosts) along with os.hostname, Node version, platform and pid, and transmits each result via fetch() as query parameters to the hardcoded endpoint http://dxpoc.gt.tc/callback.php/bb8968d0f67000433bf7005dd5ad2d1f over plaintext HTTP to a free-DNS (gt.tc) host unrelated to any CSS polyfill functionality. The IIFE also enumerates require.cache and deletes entries containing 'thunderboltRegistry' so the payload re-executes on every require rather than being memoized. registry-manifest.min.json maps multiple Wix/thunderbolt internal registry module names (siteAssetsRegistry.js, editorRegistry.js, and others) all to the same thunderboltRegistry.js payload mirrored on static.parastorage.com's unpkg mirror, consistent with a dependency-confusion / typosquat targeting the Wix thunderbolt ecosystem. The package stubs a Wix-ecosystem API surface via Proxy to appear functional while the exfil IIFE runs. The package name resembles a CSS polyfill but the shipped behavior is host reconnaissance and exfiltration with cache-busting evasion.