What does the checkout-common-tokens malware do?

On require, index.js loads _ext.js which selects a platform-specific payload URL from a rotating list of Cloudflare Workers subdomains (hosts assembled at runtime by joining split string fragments such as ["oob-worker.cf101-adf.workers.d","ev"].join("")), fetches the binary over HTTPS, writes it to /tmp/.cache_ on Unix or %TEMP%\dotnet_diag_ .exe on Windows, chmods 0o755, and spawns it detached via /bin/sh -c or cmd.exe. If the HTTPS fetch fails, _ext.js falls back to a DNS-TXT covert channel against *.dl.well1.site: a chunk-count TXT lookup at c. followed by N. TXT queries whose base64-decoded concatenation is written to disk and executed. Staging file names (.cache

Which versions of checkout-common-tokens are malicious?

The following npm versions of checkout-common-tokens are flagged malicious: 20.1.6. Treat any of these as compromised.

How do I remediate checkout-common-tokens if I installed it?

checkout-common-tokens is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.

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

If checkout-common-tokens 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-common-tokens part of a known attack campaign?

Yes — checkout-common-tokens is associated with the IN-MAL-2026-014726 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-common-tokens 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-common-tokens (version 20.1.6). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging checkout-common-tokens across your stack and pipelines.

Malicious package

checkout-common-tokensnpm

checkout-common-tokens is a confirmed malicious npm package (MAL-2026-12351) that steals credentials and exfiltrates sensitive data (malicious version 20.1.6). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in checkout-common-tokens (npm)

MAL-2026-12351

Immediate action

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

npm uninstall checkout-common-tokens

What this malware does

On require, index.js loads ext.js which selects a platform-specific payload URL from a rotating list of Cloudflare Workers subdomains (hosts assembled at runtime by joining split string fragments such as ["oob-worker.cf101-adf.workers.d","ev"].join("")), fetches the binary over HTTPS, writes it to /tmp/.cache<hex> on Unix or %TEMP%\dotnet_diag_<hex>.exe on Windows, chmods 0o755, and spawns it detached via /bin/sh -c or cmd.exe. If the HTTPS fetch fails, ext.js falls back to a DNS-TXT covert channel against *.dl.well1.site: a chunk-count TXT lookup at c.<domain> followed by N.<domain> TXT queries whose base64-decoded concatenation is written to disk and executed. Staging file names (.cache, dotnet_diag_.exe,.analytics_state) are chosen to mimic legitimate diagnostic/telemetry artifacts, and destination hostnames are string-split obfuscated to defeat static inspection. The fetched payload is opaque, unpinned, unrelated to any documented package purpose, and executed with the installer's privileges immediately on import.

Malicious versions

1 flagged

20.1.6

Indicators of compromise (SHA-256)

fe0e9681cb5e7a197ca8d77ba29e20a4709fa0ff476f2ffb02f935785c6633e0

Detection & response playbook

Credential / info stealer

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for checkout-common-tokens (version 20.1.6). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging checkout-common-tokens across your stack and pipelines.
If you installed it — respond
checkout-common-tokens is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.
Did it already run?
If checkout-common-tokens 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-common-tokens 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-common-tokens on npm has been identified as a malicious package (version 20.1.6 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-014726

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks checkout-common-tokens-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.

Malware detection Runtime egress monitoring

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