# MAL-2026-17481: Malicious code in css-light-dark-polyfill (npm)


- **Type:** Malicious package
- **Package:** `css-light-dark-polyfill` (npm)
- **Published:** 4 Oct 2026

## What is MAL-2026-17481?

MAL-2026-17481 is a malicious package in css-light-dark-polyfill, published on 4 Oct 2026. 

### Official description

The package presents itself as a trivial CSS polyfill (index.js exports an empty object) but ships thunderboltRegistry.js, which on load runs a self-invoking IIFE that collects host identifiers (os.hostname, node version, platform, pid) and the output of local shell commands (id, whoami, uname -a, ifconfig/ip addr, /etc/hosts via child_process.execSync) and POSTs each result via fetch() to the hardcoded endpoint https://dxpoc.gt.tc/callback.php/. The payload self-labels as 'beacon=rce-poc'. The package also exports factories under the names of internal Wix Thunderbolt build registries (thunderboltRegistry, siteAssetsRegistry, documentManagementRegistry, editorRegistry, etc.), and a bundled registry-manifest.min.json maps those names to parastorage.com URLs — a dependency-confusion shape targeting Wix-like build systems that resolve these internal registry module names. Installing or loading this package causes host reconnaissance data to be exfiltrated to an attacker-controlled domain unrelated to any CSS polyfill functionality.

## What should I do about MAL-2026-17481?

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-2026-17481 is a malicious package: css-light-dark-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-2026-17481/ (Markdown: https://insights.sbomify.com/MAL-2026-17481/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-17481

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-17481/
Summaries are generated and may contain mistakes; the official description above is the record.