MAL-2026-12158 Malicious code in bigops-chats-client (npm)

On require() of the package, index.js loads init.js which performs OS/arch detection, downloads a native binary from hardcoded Cloudflare Workers endpoints (oob-worker.cf101-adf.workers.dev, oob-worker.cf99-9b3.workers.dev, oob-worker.cf102-baf.workers.dev), writes it to a temp path with a masqueraded filename (e.g. dotnet_diag.exe,.cache_), chmods 0755 on Unix, and spawns it detached via /bin/sh -c or cmd.exe /c start /b. C2 hostnames are assembled at runtime from arrays of substrings joined together to evade static string search. If HTTPS retrieval fails, _init.js falls back to a DNS-TXT covert channel under *.dl.wel1.ru sub-zones (sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, net.dl.wel1.ru): it resolves c.<domain> to obtain a chunk count, resolves <i>.<domain> for each chunk, base64-decodes the concatenated payload, writes it to disk and executes it. A cache flag (.analytics_state) is used to run once per TTL. The package advertises itself as a chats client SDK; there is no legitimate reason for such a package to fetch and execute an opaque native binary at load time.