Which versions of contoso-login-sim-loader are malicious?

The following npm versions of contoso-login-sim-loader are flagged malicious: 1.0.1. Treat any of these as compromised.

How do I remediate contoso-login-sim-loader if I installed it?

contoso-login-sim-loader 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 contoso-login-sim-loader — how do I know if it already compromised me?

If contoso-login-sim-loader 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 contoso-login-sim-loader part of a known attack campaign?

Yes — contoso-login-sim-loader is associated with the IN-MAL-2026-020808 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 contoso-login-sim-loader across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for contoso-login-sim-loader (version 1.0.1).

Malicious package

contoso-login-sim-loadernpm

Advisory published Sep 30, 2026Updated Sep 30, 2026

contoso-login-sim-loader is a confirmed malicious npm package (MAL-2026-17322) that steals credentials and exfiltrates sensitive data (malicious version 1.0.1). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in contoso-login-sim-loader (npm)

MAL-2026-17322

Immediate action

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

npm uninstall contoso-login-sim-loader

What this malware does

Package ships a single ~138 KB browser script whose entire body is an RC4-encrypted base64 blob decoded at runtime by an inline RC4 routine (_zc) with a DJB2 helper (_zh) and a key reconstructed by XORing a numeric array with 1410^714. Before decryption the script performs anti-analysis guards: a devtools-size heuristic (if(_gz>160||_gp>160)return;) that aborts execution when developer tools are open, and a block that overwrites console.log/info/warn/debug/error to no-ops to suppress runtime tracing. The package name contoso-login-sim-loader self-describes as a 'login sim(ulator) loader' while the published description reframes it as a generic 'Client-side asset loader that renders a self-contained UI component when included via a script tag.' The tarball ships no source, no exports, no dependencies, and no documentation - only the opaque encrypted payload. Any site that follows the include-via-script-tag guidance embeds attacker-controlled JavaScript, decrypted only in end-user browsers, into its own pages; the concealed payload cannot be audited without executing it, and the name plus cover-story description are consistent with a fake-login/credential-harvest overlay served to that site's visitors.

Malicious versions

1 flagged

1.0.1

Indicators of compromise (SHA-256)

062ce76699c91a883d24e3ad609bb04faa3f52cbeaecfb24c1c3bcde8b496a5c

Detection & response playbook

Credential / info stealer

Find it
Search your lockfiles and build artifacts for contoso-login-sim-loader (version 1.0.1).
If you installed it — respond
contoso-login-sim-loader 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 contoso-login-sim-loader 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. contoso-login-sim-loader on npm has been identified as a malicious package (version 1.0.1 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-020808

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks contoso-login-sim-loader-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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