Which versions of css-ayucyz-polyfill are malicious?

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

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

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

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

Yes — css-ayucyz-polyfill is associated with the IN-MAL-2026-021016 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-ayucyz-polyfill across my projects, lockfiles, and CI pipelines?

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

Malicious package

css-ayucyz-polyfillnpm

Advisory published Oct 5, 2026Updated Oct 5, 2026

css-ayucyz-polyfill is a confirmed malicious npm package (MAL-2026-17548) 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-ayucyz-polyfill (npm)

MAL-2026-17548

Immediate action

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

npm uninstall css-ayucyz-polyfill

What this malware does

On require, thunderboltRegistry.js runs an IIFE that acquires child_process via multiple fallbacks and executes shell commands (id, whoami, uname -a, ifconfig/ip addr, cat /etc/hosts), then GETs the collected output along with the hostname, platform and Node version to the hardcoded plain-HTTP endpoint http://dxpoc.gt.tc/callback.php/bb8968d0f67000433bf7005dd5ad2d1f. One of the beacons is self-labeled beacon=rce-poc. The package presents itself as a CSS polyfill and exposes modules named thunderboltRegistry, siteAssetsRegistry, editorRegistry and corvidRegistry — internal Wix Thunderbolt names — behind a Proxy returning no-op functions, with registry-manifest.min.json pointing fake entries at a static.parastorage.com URL, so a consumer that resolves this package in place of the real Wix internals loads the exfiltration IIFE while the facade silently returns no-ops.

Malicious versions

1 flagged

1.0.0

Indicators of compromise (SHA-256)

d8c7540d3981f510255434529f76a2ed9a24b0783e7e8e3369b41f71b93ebd1a

Detection & response playbook

Credential / info stealer

Find it
Search your lockfiles and build artifacts for css-ayucyz-polyfill (version 1.0.0).
If you installed it — respond
css-ayucyz-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-ayucyz-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-ayucyz-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-2026-021016

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks css-ayucyz-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

All malware advisories How O3 detects malware Vulnerability database