MAL-2026-13368 Malicious code in express-dever (npm)

[email protected] registers postinstall: node index.js in package.json, and index.js is heavily obfuscated (obfuscator.io-style rotated string array with RC4/base64 decoders, hex-numeric constant folding, _0x variable naming, control-flow flattening). Decoded, the script requires axios/fs/path/child_process/os, constructs a dotted-quad host string at runtime via repeated .concat(x, '.') calls, performs axios.get(<url>), writes the response body to a file under process.cwd() with {flag:'w+'}, and spawns the written file via child_process with windowsHide:true. This is a download-and-execute dropper that fires automatically on npm install. Corroborating signals: package.json declares a self-referential floating dependency (express-dever: ^5.1.7), author and description fields are blank, and the README instructs readers to sandbox the file — consistent with a throwaway malicious upload rather than a legitimate library.