What does the checkout-context malware do?

On require, _helpers.js reassembles hostnames via array split-and-join to hide the destinations (oob-worker.cf*.workers.dev and *.dl.wel1.ru subdomains including sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, net.dl.wel1.ru), downloads a platform-specific binary via https.get, writes it to a temp path with a diagnostic-looking name (dotnet_diag_ .exe on Windows,.cache_ on Unix), chmods it 0755, and spawns it detached via /bin/sh or cmd. A persistence flag file named.analytics_state is written by helper _l. If HTTPS delivery fails, the loader falls back to a DNS TXT covert channel: resolveTxt('c.'+domain) gives a chunk count, then i.'+domain records are concatenated and base64-decod

Which versions of checkout-context are malicious?

The following npm versions of checkout-context are flagged malicious: 35.5.4. Treat any of these as compromised.

How do I remediate checkout-context if I installed it?

Remove checkout-context 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.

I already installed checkout-context — how do I know if it already compromised me?

If checkout-context 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.

Is checkout-context part of a known attack campaign?

Yes — checkout-context is associated with the IN-MAL-2026-015227 campaign. Packages in the same campaign often share infrastructure and payloads, so check whether any related packages are also in your dependency tree.

How do I find checkout-context across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for checkout-context (version 35.5.4).

Malicious package

checkout-contextnpm

Advisory published Aug 5, 2026Updated Aug 5, 2026

checkout-context is a confirmed malicious npm package (MAL-2026-12550) that executes malicious code on install (malicious version 35.5.4). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in checkout-context (npm)

MAL-2026-12550

Immediate action

Remove the package, then rotate any secrets the build/runtime could reach.

npm uninstall checkout-context

What this malware does

On require, helpers.js reassembles hostnames via array split-and-join to hide the destinations (oob-worker.cf*.workers.dev and *.dl.wel1.ru subdomains including sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, net.dl.wel1.ru), downloads a platform-specific binary via https.get, writes it to a temp path with a diagnostic-looking name (dotnet_diag<hex>.exe on Windows,.cache_<hex> on Unix), chmods it 0755, and spawns it detached via /bin/sh or cmd. A persistence flag file named.analytics_state is written by helper _l. If HTTPS delivery fails, the loader falls back to a DNS TXT covert channel: resolveTxt('c.'+domain) gives a chunk count, then i.'+domain records are concatenated and base64-decoded into the executable payload. The stated purpose of the package (a checkout context wrapper) has no relation to fetching and executing native binaries.

Malicious versions

1 flagged

35.5.4

Indicators of compromise (SHA-256)

29b244ec0b7c63b76c59ceef313391742ea858b300088653f5da701db9ca7611

Detection & response playbook

Malicious package

Find it
Search your lockfiles and build artifacts for checkout-context (version 35.5.4).
If you installed it — respond
Remove checkout-context 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.
Did it already run?
If checkout-context 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-context on npm has been identified as a malicious package (version 35.5.4 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015227

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks checkout-context-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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