MAL-2026-12779 Malicious code in devplatform-spa-plugin-s3-module-loader (npm)

On require of the package's main entry, index.js loads adapter.js, which selects a platform-specific payload URL, fetches opaque bytes from one of three obfuscated Cloudflare Workers hosts (oob-worker.cf102-baf.workers.dev, oob-worker.cf103-070.workers.dev, oob-worker.cf99-9b3.workers.dev) assembled from split string arrays, writes them to a hidden temp path (dot-file on Unix, dotnet_diag*.exe on Windows), chmods 0755 on Unix, and spawns the file detached via /bin/sh -c or cmd.exe /c start. A DNS-over-TXT fallback resolves c.<domain>/i.<domain> under sdk.dl.wel1.ru, ext.dl.wel1.ru, pkg.dl.wel1.ru, and net.dl.wel1.ru and base64-reassembles a payload from numbered TXT records when HTTPS delivery is blocked. Destinations, delivery channels, and payloads are fully author-controlled, obfuscated via runtime string reassembly, and unrelated to the package's advertised S3-module-loader purpose. Cover-story identifiers include analytics_state and DISABLE_TELEMETRY.

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.