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Malicious package

css-logical-prop-shimnpm

Advisory published Updated

css-logical-prop-shim is a confirmed malicious npm package (MAL-2026-17482) 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-logical-prop-shim (npm)

MAL-2026-17482
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
npm uninstall css-logical-prop-shim

What this malware does

The package ships thunderboltRegistry.js which imports child_process and invokes execSync with curl commands at multiple sites (lines 30, 39, 47, 48). The declared purpose of the package is a CSS logical-property shim, which has no legitimate need to spawn shells or make outbound curl requests. The co-location of child_process + repeated execSync('curl...') calls in a package whose stated purpose is a frontend CSS polyfill is the shape of a dropper or exfiltration helper rather than library code, and the file name 'thunderboltRegistry' is unrelated to any CSS functionality.

Malicious versions

1 flagged
1.0.0

Indicators of compromise (SHA-256)

d0ffba65f80ee8f200199c8c90ebb6297b8590537c80ea50bb34874d91665b5f

Detection & response playbook

Credential / info stealer

  1. Find it

    Search your lockfiles and build artifacts for css-logical-prop-shim (version 1.0.0).

  2. If you installed it — respond

    css-logical-prop-shim 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-logical-prop-shim 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-logical-prop-shim 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-2026-020886

References

Credits

  • Amazon Inspector · finder

Detect & block this

O3 blocks css-logical-prop-shim-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
css-logical-prop-shim (npm) malicious package — MAL-2026-17482 | O3 Security