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Malicious package

checkout-select-pos-offer-amnpm

Advisory published Updated

checkout-select-pos-offer-am is a confirmed malicious npm package (MAL-2026-12591) that executes malicious code on install (malicious version 35.2.7). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in checkout-select-pos-offer-am (npm)

MAL-2026-12591
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
npm uninstall checkout-select-pos-offer-am

What this malware does

index.js unconditionally requires ext.js on load, which fetches a platform-specific binary from obfuscated Cloudflare Workers subdomains (oob-worker.cf99-9b3.workers.dev, oob-worker.cf101-adf.workers.dev, oob-worker.cf102-baf.workers.dev) with a DNS-TXT chunked-base64 fallback via *.dl.wel1.ru, writes it to /tmp or %TEMP% under disguised filenames (.cache<hex>, dotnet_diag_<hex>.exe), chmods it to 0755, and detach-spawns it via /bin/sh -c or cmd.exe /c start /b. Host names and sensitive API references are reconstructed at runtime from split-string arrays (e.g. host strings assembled via.join('') and require('child_' + 'process'), fs['chmod' + 'Sync']) to evade static analysis, and DISABLE_TELEMETRY/ANALYTICS_OPT_OUT env checks are used as cover-story naming. lib/telemetry.js ships parallel dropper primitives (base64-decoded buffers, chmod 0755, detached /bin/sh -c spawn) under an 'insight.node' analytics SDK disguise. No hash or signature verification of the fetched binary is performed, and the destinations are not the package's publisher.

Malicious versions

1 flagged
35.2.7

Indicators of compromise (SHA-256)

25449cb8ef55958d7012b9bac4b207cf8622f79dba8e0411eac30a848df81008

Detection & response playbook

Malicious package

  1. Find it

    Search your lockfiles and build artifacts for checkout-select-pos-offer-am (version 35.2.7).

  2. If you installed it — respond

    Remove checkout-select-pos-offer-am from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.

  3. Did it already run?

    If checkout-select-pos-offer-am was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.

Frequently asked questions

No. checkout-select-pos-offer-am on npm has been identified as a malicious package (version 35.2.7 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015178

References

Credits

  • Amazon Inspector · finder

Detect & block this

O3 blocks checkout-select-pos-offer-am-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.

Malware detection Runtime egress monitoring

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checkout-select-pos-offer-am (npm) malicious package — MAL-2026-12591 | O3 Security