Which versions of checkout-storybook-default are malicious?

The following npm versions of checkout-storybook-default are flagged malicious: 35.5.1. Treat any of these as compromised.

How do I remediate checkout-storybook-default if I installed it?

checkout-storybook-default establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.

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

If checkout-storybook-default 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-storybook-default part of a known attack campaign?

Yes — checkout-storybook-default is associated with the IN-MAL-2026-015180 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-storybook-default across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for checkout-storybook-default (version 35.5.1).

Malicious package

checkout-storybook-defaultnpm

Advisory published Aug 5, 2026Updated Aug 5, 2026

checkout-storybook-default is a confirmed malicious npm package (MAL-2026-12593) that opens a backdoor for remote access (malicious version 35.5.1). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in checkout-storybook-default (npm)

MAL-2026-12593

Immediate action

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

npm uninstall checkout-storybook-default

What this malware does

On require of the package, index.js loads polyfill.js which reconstructs Command-and-control hostnames at runtime from split string arrays (e.g. oob-worker.cf10{0-3}-*.workers.dev), selects a platform-specific endpoint, downloads an opaque binary over HTTPS with a spoofed node-fetch User-Agent, and falls back to a chunked DNS-TXT covert channel via *.dl.wel1.ru hosts (e.g. sdk.dl.wel1.ru). The payload is written to a hidden cache path under /tmp or %TEMP% with a decoy filename (.cache<rnd> on POSIX, dotnet_diag_<rnd>.exe on Windows), chmodded 0755, and spawned detached via /bin/sh or cmd. A marker file recording process.pid gates re-execution, and opt-out env-var checks provide sandbox evasion. The behavior has no relation to the package's stated purpose.

Malicious versions

1 flagged

35.5.1

Indicators of compromise (SHA-256)

844d8b490d431f2fad501a06bbcf924fe5890ba16c92157dd52488c1908f7909

Detection & response playbook

Backdoor / remote access

Find it
Search your lockfiles and build artifacts for checkout-storybook-default (version 35.5.1).
If you installed it — respond
checkout-storybook-default establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.
Did it already run?
If checkout-storybook-default 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-storybook-default on npm has been identified as a malicious package (version 35.5.1 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015180

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks checkout-storybook-default-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.

Malware detection Runtime egress monitoring

Explore

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