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Malicious package

css-env-function-shimnpm

Advisory published Updated

css-env-function-shim is a confirmed malicious npm package (MAL-2026-17477) 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-env-function-shim (npm)

MAL-2026-17477
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
npm uninstall css-env-function-shim

What this malware does

Package self-describes as a CSS env() shim but ships thunderboltRegistry.js, which runs an IIFE at module load that base64-decodes the strings 'child_process' and 'execSync', dynamically requires child_process, and shells out whoami, uname, cat /etc/hosts, ifconfig/ip addr, id, and hostname. The collected output is POSTed to a hardcoded webhook.site URL (webhook.site/0492a36c-4d7b-408a-865c-226db25987ba) and beaconed to a subdomain of davdpb8lhot13kgmnhp0863x9g83mpswq.oast.live for DNS exfiltration. All sensitive identifiers (module name, method name, commands, destination host, UUID path, OAST subdomain) are stored as base64 blobs or String.fromCharCode arrays and reconstructed at runtime to defeat static inspection. index.js is a stub; the module factory is re-exported under nine Wix-internal registry key names (thunderboltRegistry, siteAssetsRegistry, editorRegistry, corvidRegistry, and similar), and the shipped registry-manifest.min.json aliases numerous Wix thunderbolt *Registry.js URLs on parastorage.com to this package's thunderboltRegistry.js — a dependency-confusion lure targeting Wix's internal build so that any importer of those names triggers the exfiltration IIFE at require time.

Malicious versions

1 flagged
1.0.0

Indicators of compromise (SHA-256)

03e6fced50259d6d3781ef3917caba965e4744420188c3e06919541b64e2e294

Detection & response playbook

Credential / info stealer

  1. Find it

    Search your lockfiles and build artifacts for css-env-function-shim (version 1.0.0).

  2. If you installed it — respond

    css-env-function-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-env-function-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-env-function-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-2026-020884

References

Credits

  • Amazon Inspector · finder

Detect & block this

O3 blocks css-env-function-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-env-function-shim (npm) malicious package — MAL-2026-17477 | O3 Security