MAL-2026-10189 Malicious code in tinymask-js (npm)

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.

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.