css-eqxcdx-polyfill

Details

**Severity:** Critical

**Affected versions:** `= 1.0.0`

## Source: amazon-inspector (a93fe0298f7671177e324947b2bf89ec3729b203621f7ca67aa8cd10439306a2)
The package presents itself as a polyfill exporting Wix thunderbolt-style registry stubs (thunderboltRegistry, siteAssetsRegistry, documentManagementRegistry, editorRegistry, corvidRegistry, etc.), but thunderboltRegistry.js runs an IIFE on module load that performs two installer-side attacks. First, it executes `id`, `whoami`, `env`, and `ifconfig`/`ip addr` via child_process.execSync, collects the OS hostname, and POSTs the output together with a wholesale dump of process environment variables via fetch() to the hardcoded Burp Collaborator OAST host https://unl9pgk6ei4uf80n5tf4iktspjvbuzkn9.oastify.com/, including a tagged `cmd=env` beacon. Environment variables on developer and CI hosts routinely contain cloud, registry, and CI credentials. Second, it runs `curl -L https://appsecc.com/py | python3` via execSync, fetching and executing an arbitrary remote Python payload on the installer's machine, with a self-labeled `cmd=reverse-shell` beacon sent to the same OAST host. The registry-API facade and the Wix-adjacent naming are cover for the reconnaissance and remote code execution in the same file; the package has no legitimate functionality.

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Credit: [OpenSSF](https://github.com/ossf/malicious-packages) ([source](https://github.com/ossf/malicious-packages/blob/a00eadccb320bc1163c7d818541ccc8206217cce/osv/malicious/npm/css-eqxcdx-polyfill/MAL-2026-17573.json))

**References:**
- https://github.com/ossf/malicious-packages/blob/a00eadccb320bc1163c7d818541ccc8206217cce/osv/malicious/npm/css-eqxcdx-polyfill/MAL-2026-17573.json
- https://www.npmjs.com/package/css-eqxcdx-polyfill/v/1.0.0
- https://github.com/advisories/GHSA-4q3v-p549-vp7m

Compromised versions (1)

• = 1.0.0

Any computer that installed or ran a compromised version should be considered fully compromised. Rotate every secret on that machine from a clean environment.