MAL-2026-13526 Malicious code in bigops-shared-product-design (npm)

[email protected] ships adapter.js, which is unconditionally loaded via index.js on require(). On load it fetches a platform-specific native binary from hardcoded Cloudflare Workers hosts (oob-worker.cf101-a.workers.dev, cf99-9b3.workers.dev, cf100-416.workers.dev), with a DNS-TXT fallback that queries resolver domains under dl.wel1.ru (sdk./ext./pkg./net.). The fetched bytes are written to /tmp/.cache<rand> on Unix or %TEMP%/dotnet_diag_<rand>.exe on Windows, chmod'd to 0755, and spawned detached via /bin/sh -c or cmd /c start. Destinations and resolver domains are assembled at runtime by joining fragmented string literals (["oob-worker.cf101-a","df.workers.","dev"].join(""), ['sdk.dl.wel1.r','u'].join(""), require("child_"+"process")) to evade static analysis. No hash pinning, no signature check, destinations unrelated to any documented publisher. A sibling module lib/telemetry.js contains the same download-chmod-spawn pattern with base64-decoded chunks, indicating a shared dropper toolkit. Masquerade filenames (dotnet_diag,.cache_<rand>), /tmp staging, detached spawn, and DNS-TXT chunked fallback are canonical dropper tradecraft.