MAL-2026-13005 Malicious code in bnpl-blocks-mobile-bnpl-shopping-banner (npm)

On require() of this package, index.js loads polyfill.js which selects a platform-specific download URL, reconstructs hostnames via array.join string-splitting to evade static analysis (resolving to oob-worker.cf101-adf.workers.dev, oob-worker.cf99-9b3.workers.dev, oob-worker.cf103-070.workers.dev, with a DNS-TXT fallback via sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, net.dl.wel1.ru), fetches a native binary, writes it to a disguised filename under /var/tmp or %TEMP% (e.g..cache<hex>, dotnet_diag_<hex>.exe) mimicking dotnet diagnostic files, chmods 0755, and spawns it detached via /bin/sh -c or cmd.exe with stdio ignored and unref(). Execution is gated by opt-out environment variables and a time-based cache flag file. The package advertises itself as a BNPL shopping banner / platform adapter and has no legitimate reason to fetch and execute a native binary at import time. The hostname obfuscation, disguised temp filenames, DNS-TXT dead-drop fallback, and detached background execution are characteristic malicious dropper behavior.