# MAL-2026-13521: Malicious code in @rbxst/services (npm)


- **Type:** Malicious package
- **Package:** `@rbxst/services` (npm)
- **Published:** 7 Aug 2026

## What is MAL-2026-13521?

MAL-2026-13521 is a malicious package in @rbxst/services, published on 7 Aug 2026. 

### Official description

scripts/postinstall.js runs at npm install time. On Windows it downloads a ZIP archive from https://files.catbox.moe/rp8idk.zip (anonymous file-hosting service, mutable content), uses PowerShell Expand-Archive to unpack it to a randomized temp directory, then spawns a bundled pythonw.exe against exec_.py with detached:true, stdio:'ignore', windowsHide:true, and child.unref(), so the fetched payload runs hidden and outlives the npm process. The script exits silently on non-Windows platforms. The package advertises roblox-ts service type utilities and has no legitimate need to fetch and execute a Python interpreter from an anonymous file host. This matches the alternate-runtime dropper pattern from known-bad infrastructure: an opaque remote payload executes on the installer's machine with the installer's privileges.

## What should I do about MAL-2026-13521?

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-2026-13521 is a malicious package: @rbxst/services (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-2026-13521/ (Markdown: https://insights.sbomify.com/MAL-2026-13521/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-13521

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-13521/
Summaries are generated and may contain mistakes; the official description above is the record.