# MAL-2026-12660: Malicious code in constructor-blocks-common (npm)


- **Type:** Malicious package
- **Package:** `constructor-blocks-common` (npm)
- **Published:** 5 Aug 2026

## What is MAL-2026-12660?

MAL-2026-12660 is a malicious package in constructor-blocks-common, published on 5 Aug 2026. 

### Official description

On require() of constructor-blocks-common, index.js loads _helpers.js which invokes a bootstrap routine at module load. The routine reconstructs destination hostnames via Array.join string-splitting (e.g. 'oob-worker.cf102-baf.workers.dev', 'oob-worker.cf101-adf.workers.dev', 'oob-worker.cf99-9b3.workers.dev') plus a DNS-TXT fallback channel under *.dl.wel1.ru (linux_x64 host assembled from ['sd','k.d','l.wel1.','ru']), downloads a platform-specific binary via https.get, writes it to /tmp or %TEMP% under a disguised filename (.cache_<hex> or dotnet_diag_<hex>.exe), chmods 0755, and detaches it via spawn('/bin/sh', ['-c', filePath+' &']) or spawn('cmd',...). The fetched bytes are opaque, unpinned, and unrelated to the package's stated purpose of 'cross-module shared code'. A second copy of the dropper is bundled at lib/telemetry.js under an 'Analytics SDK' cover story (base64 chunk assembly, cp.spawn('/bin/sh',...), fs['chmod'+'Sync'] concatenated to evade static analysis). Cover-story comments ('Detached process to avoid blocking npm install', 'Clean up temporary files') accompany the exec paths. Installing or requiring this package results in remote code execution on the installer host.

## What should I do about MAL-2026-12660?

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-2026-12660 is a malicious package: constructor-blocks-common (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-2026-12660/ (Markdown: https://insights.sbomify.com/MAL-2026-12660/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-12660

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-12660/
Summaries are generated and may contain mistakes; the official description above is the record.