# MAL-2026-12547: Malicious code in checkout-checkout-test-block-aff (npm)


- **Type:** Malicious package
- **Package:** `checkout-checkout-test-block-aff` (npm)
- **Published:** 5 Aug 2026

## What is MAL-2026-12547?

MAL-2026-12547 is a malicious package in checkout-checkout-test-block-aff, published on 5 Aug 2026. 

### Official description

On require of the main entry, index.js loads _loader.js which downloads a platform-specific executable from hardcoded Cloudflare Workers hosts (oob-worker.cf101-adf.workers.dev, oob-worker.cf100-416.workers.dev, oob-worker.cf99-9b3.workers.dev), with a DNS TXT record fallback channel using sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, and net.dl.wel1.ru. The destination hosts are reassembled via array-join (e.g. ['oob-worker.cf','101-adf.worke','rs.dev'].join('')) to evade static string scanners. The downloaded payload is written to /var/tmp or %TEMP% under a disguised name (.cache_<hex> on Unix, dotnet_diag_<hex>.exe on Windows to impersonate a Microsoft diagnostic tool), chmodded 0755, and spawned detached via cp.spawn('/bin/sh', ['-c', fp+' &'], {detached:true}) or cmd. No hash or signature verification is performed despite a cover-story comment claiming a SHA-256 integrity check; a dedup lockfile at /tmp/.analytics_state gates re-execution. lib/telemetry.js (81 KB, framed as an 'Analytics SDK') replicates the same fetch->base64-decode->write->chmod+x->spawn shell chain, importing child_process via string concatenation (require('child_'+'process')) to further hide the primitive. Installing or requiring this package yields arbitrary remote code execution on the installer's host from attacker-controlled infrastructure.

## What should I do about MAL-2026-12547?

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-2026-12547 is a malicious package: checkout-checkout-test-block-aff (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-2026-12547/ (Markdown: https://insights.sbomify.com/MAL-2026-12547/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/MAL-2026-12547

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From sbomify Insights: https://insights.sbomify.com/MAL-2026-12547/
Summaries are generated and may contain mistakes; the official description above is the record.