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

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

--- _-= Per source details. Do not edit below this line.=-_ ## Source: amazon-inspector (062ce76699c91a883d24e3ad609bb04faa3f52cbeaecfb24c1c3bcde8b496a5c) 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.

Source published

30 Sep 2026 04:40:31 UTC

Source modified

30 Sep 2026 05:00:08 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.