What does the checkout-subscription-holder malware do?

On require() of the package, index.js loads _bootstrap.js inside a try/catch. _bootstrap.js reconstructs its download hosts via array.join("") string-splitting (assembling oob-worker.cf{101-adf,99-9b3,103-070,102-baf}.workers.dev and a *.dl.wel1.ru DNS-TXT base64 fallback resolver), downloads a platform-specific opaque binary, writes it to /var/tmp/.cache_ on POSIX or TEMP\dotnet_diag_ .exe on Windows, chmods it 0755, and spawns it detached via /bin/sh -c or cmd.exe. Filenames are chosen to masquerade as a dotnet diagnostic tool or generic cache, and a /tmp/.analytics_state marker gates re-execution. The advertised package purpose ("subscription holder") has no connection to the fet

Which versions of checkout-subscription-holder are malicious?

The following npm versions of checkout-subscription-holder are flagged malicious: 35.7.1. Treat any of these as compromised.

How do I remediate checkout-subscription-holder if I installed it?

Remove checkout-subscription-holder 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-subscription-holder — how do I know if it already compromised me?

If checkout-subscription-holder 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-subscription-holder part of a known attack campaign?

Yes — checkout-subscription-holder is associated with the IN-MAL-2026-015187 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-subscription-holder 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-subscription-holder (version 35.7.1). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging checkout-subscription-holder across your stack and pipelines.

Malicious package

checkout-subscription-holdernpm

checkout-subscription-holder is a confirmed malicious npm package (MAL-2026-12594) that executes malicious code on install (malicious version 35.7.1). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in checkout-subscription-holder (npm)

MAL-2026-12594

Immediate action

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

npm uninstall checkout-subscription-holder

What this malware does

On require() of the package, index.js loads bootstrap.js inside a try/catch. bootstrap.js reconstructs its download hosts via array.join("") string-splitting (assembling oob-worker.cf{101-adf,99-9b3,103-070,102-baf}.workers.dev and a *.dl.wel1.ru DNS-TXT base64 fallback resolver), downloads a platform-specific opaque binary, writes it to /var/tmp/.cache<hex> on POSIX or TEMP\dotnet_diag<hex>.exe on Windows, chmods it 0755, and spawns it detached via /bin/sh -c or cmd.exe. Filenames are chosen to masquerade as a dotnet diagnostic tool or generic cache, and a /tmp/.analytics_state marker gates re-execution. The advertised package purpose ("subscription holder") has no connection to the fetched-and-executed binary, and the destination hosts are string-split constants rather than a documented, publisher-owned domain.

Malicious versions

1 flagged

35.7.1

Indicators of compromise (SHA-256)

e7a62aaa04f6806d8ad86f8c9baaaddde733815a4d2f51bc3db803bf30998f4c

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-subscription-holder (version 35.7.1). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging checkout-subscription-holder across your stack and pipelines.
If you installed it — respond
Remove checkout-subscription-holder 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-subscription-holder 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-subscription-holder 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-subscription-holder on npm has been identified as a malicious package (version 35.7.1 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015187

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks checkout-subscription-holder-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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