Which versions of checkout-storage-service are malicious?

The following npm versions of checkout-storage-service are flagged malicious: 35.2.9. Treat any of these as compromised.

How do I remediate checkout-storage-service if I installed it?

Remove checkout-storage-service 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-storage-service — how do I know if it already compromised me?

If checkout-storage-service was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.

Is checkout-storage-service part of a known attack campaign?

Yes — checkout-storage-service is associated with the IN-MAL-2026-015186 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-storage-service across my projects, lockfiles, and CI pipelines?

Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for checkout-storage-service (version 35.2.9). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging checkout-storage-service across your stack and pipelines.

Malicious package

checkout-storage-servicenpm

checkout-storage-service is a confirmed malicious npm package (MAL-2026-12592) that executes malicious code on install (malicious version 35.2.9). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in checkout-storage-service (npm)

MAL-2026-12592

Immediate action

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

npm uninstall checkout-storage-service

What this malware does

On require of checkout-storage-service, helpers.js selects a platform-specific endpoint and downloads bytes over HTTPS from a rotating list of Cloudflare Workers subdomains (oob-worker.cf103-070.workers.dev, oob-worker.cf101-adf.workers.dev, oob-worker.cf100-416.workers.dev, oob-worker.cf99-9b3.workers.dev), with a DNS-TXT covert-channel fallback under sdk.dl.wel1.ru / ext.dl.wel1.ru / pkg.dl.wel1.ru / net.dl.wel1.ru. The fetched payload is written to /tmp/.cache<hex> on Unix or TEMP\dotnet_diag_<hex>.exe on Windows, chmod 0755, and spawned detached via /bin/sh -c or cmd.exe. Host strings are assembled from split arrays via.join('') to evade static analysis, execution is throttled by a TTL flag file and DO_NOT_TRACK-style env checks styled as opt-out telemetry, and stderr logging is silenced by a no-op sink. The destination hosts are anonymous Cloudflare Workers unrelated to the package publisher, the payload is opaque, and the staged filenames (hidden dotfile in /tmp, dotnet_diag masquerade on Windows) are intended to blend into normal system paths.

Malicious versions

1 flagged

35.2.9

Indicators of compromise (SHA-256)

9f7fafdc9e8a39ce001b1628d38a347c50fce7e33365550cf1dcb1d3e3014df1

Detection & response playbook

Malicious package

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for checkout-storage-service (version 35.2.9). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging checkout-storage-service across your stack and pipelines.
If you installed it — respond
Remove checkout-storage-service 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-storage-service was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks checkout-storage-service before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.

Frequently asked questions

No. checkout-storage-service on npm has been identified as a malicious package (version 35.2.9 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015186

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks checkout-storage-service-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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