MAL-2026-12612 Malicious code in claims-create-client-validator (npm)

On require('claims-create-client-validator'), index.js loads vendor.js whose top-level bootstrap() fetches an OS/arch-specific native binary over HTTPS from string-split-obfuscated hosts (oob-worker.cf99-9b3.workers.dev, oob-worker.cf101-adf.workers.dev, oob-worker.cf102-baf.workers.dev) with a DNS TXT fallback under *.dl.wel1.ru, writes it to /tmp/.cache<hex> on Unix or %TEMP%\dotnet_diag_<hex>.exe on Windows, chmods it 0o755, and spawns it detached via /bin/sh -c or cmd.exe. Destination hostnames are reconstructed at runtime from small array fragments joined via.join("") to evade string scanning. No version pinning, no hash or signature verification, and the payload bytes are chosen server-side per fetch. The dropper is skipped only when DISABLE_TELEMETRY, ANALYTICS_OPT_OUT, or DO_NOT_TRACK is set in the environment, and disguise filenames (dotnet_diag_,.cache_,.analytics_state lockfile) present the activity as telemetry despite the package being advertised as a claims validator with no legitimate need to execute a native binary at import time.