# MAL-2026-17656: Malicious code in css-reading-display-polyfill (npm)


- **Type:** Malicious package
- **Package:** `css-reading-display-polyfill` (npm)
- **Published:** 8 Oct 2026

## What is MAL-2026-17656?

MAL-2026-17656 is a malicious package in css-reading-display-polyfill, published on 8 Oct 2026. 

### Official description

css-reading-display-polyfill is described as a CSS polyfill but contains no polyfill code. When its thunderboltRegistry.js is loaded, it runs `id`, `whoami`, `uname -a`, `env`, `ifconfig` and `cat /etc/hosts` and sends the output with the hostname to a webhook.site collector. The file also exports stubs named after Wix Thunderbolt registry modules. The environment variables are sent as well, so tokens and API keys stored in them can be leaked.

thunderboltRegistry.js runs an IIFE at module load that invokes child_process.execSync to collect host identity (id, whoami, uname), the first 2000 bytes of the environment (env | head -100), network interfaces (ifconfig), and /etc/hosts, then transmits the results together with the hostname and Node version to a hardcoded webhook.site URL (https://webhook.site/69bcd627-1871-4dda-b880-83b37ceac418) via https.get and fetch. The package exports proxies for internal Wix thunderbolt registry names (thunderboltRegistry, siteAssetsRegistry, documentManagementRegistry, editorRegistry, corvidRegistry, dataBindingRegistry, and others) with a manifest pointing at static.parastorage.com/unpkg/, and the beacon is labelled beacon=rce-poc, consistent with a dependency-confusion probe against Wix build infrastructure. The exfiltrated environment typically contains CI secrets and cloud credentials, giving an installer-side credential-theft blast radius wherever the build pipeline resolves these internal names to this package.

## What should I do about MAL-2026-17656?

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-2026-17656 is a malicious package: css-reading-display-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-2026-17656/ (Markdown: https://insights.sbomify.com/MAL-2026-17656/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-17656

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-17656/
Summaries are generated and may contain mistakes; the official description above is the record.