contoso-login-sim-loader (npm) · Malicious Code
Affects contoso-login-sim-loaderSource GCVE Database
Malicious package : remove contoso-login-sim-loader and rotate any secrets on hosts that installed it.
Data as of 30 Sep 2026, 16:39 UTC
Malicious package
Published to npm · OSV MAL-2026-17322
What to do
Remove contoso-login-sim-loader from every project, lockfile and image that pulls it in. Treat any host that installed it as compromised: rotate the credentials, tokens and keys it could read, from a clean machine.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| npmcontoso-login-sim-loader | Affected
| Fixed in– |
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Description
The contoso-login-sim-loader npm package contains a malicious payload concealed as an RC4-encrypted base64 blob that decrypts and executes in the browser at runtime. It employs anti-analysis techniques such as detecting developer tools and disabling console logging to evade detection. The package lacks source code, dependencies, or documentation, and its deceptive naming and description suggest it may serve as a fake login or credential-harvesting overlay when included in websites. This behavior poses a risk of embedding attacker-controlled JavaScript into affected sites, potentially compromising end users.