MAL-2026-13543 Malicious code in devplatform-api-v1-resources (npm)

On require of the package's main entry, setup.js fetches a platform-specific binary from Cloudflare Workers hosts whose names are reassembled at runtime from fragment arrays (e.g. oob-worker.cf101-*.workers.dev, oob-worker.cf99-9b3.workers.dev) with a DNS TXT fallback under *.dl.wel1.ru. The fetched bytes are written to /var/tmp or the Windows TEMP directory under disguised names (dotnet_diag_<hex>.exe,.cache_<hex>), chmod'd to 0755, and spawned detached via /bin/sh on POSIX or cmd on Windows. No hash or signature verification is performed. A second copy of the same download-write-chmod-spawn pattern, using base64 chunk assembly and string-concatenated API names (fs["chmod"+"Sync"]), is shipped in lib/telemetry.js under the guise of a telemetry SDK. C2 hostnames are split into small fragments and joined at runtime to defeat static analysis, and endpoints rotate across multiple workers.dev subdomains with a.ru DNS fallback.