MAL-2026-12233 Malicious code in tinkoff-boxy-independent-kasko-form (npm)

On require of the package, index.js loads bootstrap.js which reconstructs hardcoded hostnames via split-string.join obfuscation and downloads a platform-specific binary from Cloudflare Workers subdomains (oob-worker.cf101-adf.workers.dev, oob-worker.cf100-416.workers.dev, oob-worker.cf99-9b3.workers.dev, oob-worker.cf102-baf.workers.dev). If HTTPS mirrors fail, resolveDns() reads a chunk count from c.<domain> TXT records and fetches base64-encoded payload chunks from N.tin.dl.well1.site TXT records, reassembling them into an executable. The payload is written to /tmp or %TEMP% under disguised filenames (.cache<hex>, dotnet_diag_<hex>.exe), chmod 0755, and spawned detached via cp.spawn("/bin/sh", ["-c", filePath + " &"]) or cmd equivalent on Windows. The package name references an unrelated 'kasko form' library, unrelated to the dropper behavior. lib/telemetry.js ships a second copy of the same drop-and-exec logic under an 'analytics SDK' cover story.