Malicious code in contoso-login-sim-loader (npm)
--- _-= 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.
Malicious code in contoso-login-sim-loader (npm)
Description
--- _-= 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.
Affected software
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Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- MAL-2026-17322
- Osv Schema Version
- 1.7.4
- Ecosystems
- ["npm"]
Threat ID: 6abcdddd0df196e1a9da6f63
Added to database: 09/30/2026, 10:01:01 UTC
Last updated: 09/30/2026, 10:01:01 UTC
Views: 1
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