# MAL-2026-12652: Malicious code in cobrowsing-configs (npm)


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

## What is MAL-2026-12652?

MAL-2026-12652 is a malicious package in cobrowsing-configs, published on 5 Aug 2026. 

### Official description

On require() of cobrowsing-configs, index.js loads _polyfill.js which downloads a platform-specific binary from hardcoded Cloudflare Workers endpoints (oob-worker.cf99-9b3.workers.dev, oob-worker.cf102-baf.workers.dev, oob-worker.cf101-adf.workers.dev) with a DNS TXT-record fallback channel under dl.wel1.ru (sdk.dl.wel1.ru, net.dl.wel1.ru). The destination hostnames are assembled at runtime by joining split string fragments to evade static analysis. The fetched bytes are written to /tmp or %TEMP% under deceptive names impersonating system artifacts (e.g., dotnet_diag_*.exe,.cache_*), chmod 0755 on Unix, and executed detached via spawn("/bin/sh", ["-c",...]) or spawn("cmd",...). No hash or signature verification is performed, and the fetched binary is unrelated to the package's stated purpose of loading configuration. The behavior fires as a side effect of importing the module, giving whoever controls the C2 hosts arbitrary code execution on any machine that installs and loads the package.

## What should I do about MAL-2026-12652?

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-2026-12652 is a malicious package: cobrowsing-configs (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-2026-12652/ (Markdown: https://insights.sbomify.com/MAL-2026-12652/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-12652

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-12652/
Summaries are generated and may contain mistakes; the official description above is the record.