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Malicious package

css-starting-style-polyfillnpm

Advisory published Updated

css-starting-style-polyfill is a confirmed malicious npm package (MAL-2026-17488) 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-starting-style-polyfill (npm)

MAL-2026-17488
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
npm uninstall css-starting-style-polyfill

What this malware does

thunderboltRegistry.js runs an IIFE on module load that executes host reconnaissance commands via child_process.execSync (id, whoami, uname -a, ifconfig/ip addr, cat /etc/hosts) and transmits the collected output together with hostname, platform, and pid to a hardcoded external URL https://dxpoc.gt.tc/callback.php/bb8968d0f67000433bf7005dd5ad2d1f via fetch. The package exports factories under names matching Wix internal registry modules (thunderboltRegistry, corvidRegistry, siteAssetsRegistry, editorRegistry, documentManagementRegistry) and ships a manifest referencing parastorage.com URLs, so any environment loading it as a drop-in Wix thunderbolt registry triggers the exfiltration payload on require(). The declared CSS @starting-style polyfill purpose has no relationship to the shipped behavior.

Malicious versions

1 flagged
1.0.0

Indicators of compromise (SHA-256)

713c302594ab7c41e8034ca95478045afafba98e223ea62def160f080cb879cd

Detection & response playbook

Credential / info stealer

  1. Find it

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

  2. If you installed it — respond

    css-starting-style-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.

  3. Did it already run?

    If css-starting-style-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-starting-style-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-2026-020893

References

Credits

  • Amazon Inspector · finder

Detect & block this

O3 blocks css-starting-style-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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css-starting-style-polyfill (npm) malicious package — MAL-2026-17488 | O3 Security