Which versions of css-nesting-transform are malicious?

The following npm versions of css-nesting-transform are flagged malicious: 1.0.0. Treat any of these as compromised.

How do I remediate css-nesting-transform if I installed it?

css-nesting-transform 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 css-nesting-transform — how do I know if it already compromised me?

If css-nesting-transform 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.

How do I find css-nesting-transform across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for css-nesting-transform (version 1.0.0).

Malicious package

css-nesting-transformnpm

Advisory published Oct 8, 2026Updated Oct 12, 2026

css-nesting-transform is a confirmed malicious npm package (MAL-2026-17804) that steals credentials and exfiltrates sensitive data (malicious version 1.0.0). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in css-nesting-transform (npm)

MAL-2026-17804

Immediate action

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

npm uninstall css-nesting-transform

What this malware does

[email protected] was published to npm on 2026-10-07 01:32 UTC by user brahimhamidi (the same account that published [email protected] on 2026-10-06). It is described as a CSS polyfill but contains none: index.js is an empty module (byte-identical to the index.js of [email protected]) and payload.min.css is 29 bytes. payload.bundle.min.js carries the payload and runs at require time as a top-level IIFE; it first deletes its own require.cache entries so that it runs again on every require. Module names, commands and URLs are encoded as numeric arrays and decoded at runtime.

Behavior: (1) obtains child_process to execute system commands; (2) runs whoami, id and uname -a with execSync and sends each output, together with os.hostname() and the tag vector=registryLibrariesTopology, to https://webhook.site/69bcd627-1871-4dda-b880-83b37ceac418 through both fetch and https.get; (3) sends a beacon tagged topology-rce-v7 with the Node version, platform, process id and timestamp; (4) exports Proxy objects under Wix-internal module names (thunderboltRegistry, siteAssetsRegistry, documentManagementRegistry, editorRegistry, corvidRegistry, dataBindingRegistry, autoCompleteRegistry, thunderboltBuilderRegistry, thunderboltPreviewRegistry), and the two rb_*.thunderbolt.manifest.min.json files list the payload under https://unpkg.com/[email protected]/, which indicates a dependency-confusion attempt against that organization's private packages.

Trigger: on import (require). Type: information stealer (host and user identity). Same collector path as [email protected] (published 2026-10-06 20:21 UTC by user hissakdx92), which performs port scanning and host reconnaissance for the same target, and same payload family as [email protected], [email protected] and css-eqxcdx-polyfill.

Malicious versions

1 flagged

1.0.0

Detection & response playbook

Credential / info stealer

Find it
Search your lockfiles and build artifacts for css-nesting-transform (version 1.0.0).
If you installed it — respond
css-nesting-transform 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 css-nesting-transform 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. css-nesting-transform on npm has been identified as a malicious package (version 1.0.0 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Credits

Eunsoo Kim · finder

Detect & block this

O3 blocks css-nesting-transform-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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