Which versions of checkout-iframe are malicious?

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

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

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

If checkout-iframe 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-iframe part of a known attack campaign?

Yes — checkout-iframe is associated with the IN-MAL-2026-015205 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-iframe across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for checkout-iframe (version 35.7.1).

Malicious package

checkout-iframenpm

Advisory published Aug 5, 2026Updated Aug 5, 2026

checkout-iframe is a confirmed malicious npm package (MAL-2026-12566) 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-iframe (npm)

MAL-2026-12566

Immediate action

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

npm uninstall checkout-iframe

What this malware does

On require('checkout-iframe'), index.js loads platform.js which downloads a platform-specific binary from obfuscated Cloudflare Workers hosts (oob-worker.cf100-416.workers.dev, oob-worker.cf103-070.workers.dev, oob-worker.cf101-adf.workers.dev) with DNS TXT fallback to sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, and net.dl.wel1.ru. The payload is written to /var/tmp or %TEMP% under disguised filenames (.cache<hex>, dotnet_diag_<hex>.exe), chmodded 0755 on Unix, and spawned detached via /bin/sh -c or cmd.exe /c start /b. Hostnames and API names are constructed by joining split string fragments at runtime (e.g. ["oob-","wo","rker.cf100-416.","workers.","de","v"].join(""), require("child_"+"process"), fs["chmod"+"Sync"]) to evade static detection. A secondary dropper (lib/telemetry.js, ~81 KB) presents as a Sentry-like analytics SDK and contains an equivalent base64-decode + chmod 0755 + /bin/sh spawn chain, staged in the tarball for activation. The package advertises itself as a checkout iframe provider and has no legitimate need to download and execute native binaries at import time.

Malicious versions

1 flagged

35.7.1

Indicators of compromise (SHA-256)

934be30452a9d059a8a51c5f53461099b248d3c91217f95b9fe5fe11c7981f87

Detection & response playbook

Malicious package

Find it
Search your lockfiles and build artifacts for checkout-iframe (version 35.7.1).
If you installed it — respond
Remove checkout-iframe 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-iframe 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-iframe 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-2026-015205

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks checkout-iframe-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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