Malicious code in tinymask-js (npm)
--- _-= Per source details. Do not edit below this line.=-_ ## Source: amazon-inspector (dc1d083feee4cace9dba5cabdfd74701c7dc093520f0bbc104858ab699203604) index.js (declared as the package main) reconstructs a host, URL paths, and dropped filenames from String.fromCharCode numeric arrays, resolving to https://filament-zap.vercel.app/service/assets/fetchBinary and /fetchLinuxBinary. On require, it downloads an OS-specific binary over HTTPS, writes it to %LOCALAPPDATA%\Programs\WinMetrics\WinService.exe on Windows or ~/.local/share/WinMetrics on Linux, chmods it 0755 on Linux, and spawns it detached with stdio ignored and windowsHide set. The binary is fetched from a non-publisher host, is not pinned or hash/signature-verified, and its cover-story naming ('WinMetrics', 'WinService.exe') is unrelated to the package's advertised input-masking purpose. The package name mirrors the legitimate 'tinymask' package, declares 'tinymask': '*' as a dependency, and ends index.js with module.exports = require('tinymask'), so consumers who mistype the name receive real tinymask functionality alongside the hidden dropper.
AI Analysis
Technical Summary
The 'tinymask-js' npm package version 1.0.2 contains malicious code in its main index.js file. Upon requiring the package, it reconstructs URLs from obfuscated numeric arrays to download an OS-specific binary over HTTPS from a non-publisher-controlled host. This binary is saved to %LOCALAPPDATA%\Programs\WinMetrics\WinService.exe on Windows or ~/.local/share/WinMetrics on Linux, given executable permissions on Linux, and then spawned detached with no standard IO and hidden windows. The package name closely resembles the legitimate 'tinymask' package and exports the real 'tinymask' module to avoid suspicion, effectively acting as a trojanized package that delivers a hidden dropper alongside expected functionality.
Potential Impact
This malicious package can lead to arbitrary code execution on the affected system by downloading and running an unverified binary from an external source. The binary runs with the privileges of the user installing the package, potentially enabling unauthorized actions or persistence. The obfuscation and mimicry of a legitimate package increase the risk of inadvertent installation by developers.
Mitigation Recommendations
No official patch or fix is available for this malicious package. The recommended mitigation is to avoid using 'tinymask-js' version 1.0.2 and instead use the legitimate 'tinymask' package. Verify package names carefully before installation to prevent typosquatting attacks. Monitor package sources and use trusted registries or package signing where possible.
Malicious code in tinymask-js (npm)
Description
--- _-= Per source details. Do not edit below this line.=-_ ## Source: amazon-inspector (dc1d083feee4cace9dba5cabdfd74701c7dc093520f0bbc104858ab699203604) index.js (declared as the package main) reconstructs a host, URL paths, and dropped filenames from String.fromCharCode numeric arrays, resolving to https://filament-zap.vercel.app/service/assets/fetchBinary and /fetchLinuxBinary. On require, it downloads an OS-specific binary over HTTPS, writes it to %LOCALAPPDATA%\Programs\WinMetrics\WinService.exe on Windows or ~/.local/share/WinMetrics on Linux, chmods it 0755 on Linux, and spawns it detached with stdio ignored and windowsHide set. The binary is fetched from a non-publisher host, is not pinned or hash/signature-verified, and its cover-story naming ('WinMetrics', 'WinService.exe') is unrelated to the package's advertised input-masking purpose. The package name mirrors the legitimate 'tinymask' package, declares 'tinymask': '*' as a dependency, and ends index.js with module.exports = require('tinymask'), so consumers who mistype the name receive real tinymask functionality alongside the hidden dropper.
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The 'tinymask-js' npm package version 1.0.2 contains malicious code in its main index.js file. Upon requiring the package, it reconstructs URLs from obfuscated numeric arrays to download an OS-specific binary over HTTPS from a non-publisher-controlled host. This binary is saved to %LOCALAPPDATA%\Programs\WinMetrics\WinService.exe on Windows or ~/.local/share/WinMetrics on Linux, given executable permissions on Linux, and then spawned detached with no standard IO and hidden windows. The package name closely resembles the legitimate 'tinymask' package and exports the real 'tinymask' module to avoid suspicion, effectively acting as a trojanized package that delivers a hidden dropper alongside expected functionality.
Potential Impact
This malicious package can lead to arbitrary code execution on the affected system by downloading and running an unverified binary from an external source. The binary runs with the privileges of the user installing the package, potentially enabling unauthorized actions or persistence. The obfuscation and mimicry of a legitimate package increase the risk of inadvertent installation by developers.
Mitigation Recommendations
No official patch or fix is available for this malicious package. The recommended mitigation is to avoid using 'tinymask-js' version 1.0.2 and instead use the legitimate 'tinymask' package. Verify package names carefully before installation to prevent typosquatting attacks. Monitor package sources and use trusted registries or package signing where possible.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- MAL-2026-10189
- Osv Schema Version
- 1.7.4
- Aliases
- []
- Ecosystems
- ["npm"]
- Database Specific Severity
- null
- Cvss Version
- null
Threat ID: 6a535bfc68715ace43ad5135
Added to database: 07/12/2026, 09:18:52 UTC
Last enriched: 07/12/2026, 09:21:00 UTC
Last updated: 07/31/2026, 08:19:15 UTC
Views: 61
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