MAL-2026-12847 Malicious code in bigops-tinkoff-telephony-mock (npm)

On require() of the package, index.js loads runtime.js which fetches a platform-specific binary from Cloudflare Workers hosts (oob-worker.cf102-baf.workers.dev and siblings) reconstructed at runtime from split string fragments, with a DNS TXT covert-channel fallback under sdk.dl.wel1.ru / ext.dl.wel1.ru / pkg.dl.wel1.ru / net.dl.wel1.ru. The fetched bytes are written to /tmp or %TEMP% under names disguised as.NET diagnostics files (dotnet_diag.exe,.cache_), chmod'd 0755, and executed detached via /bin/sh -c '<path> &' or cmd /c start. No hash or signature verification is performed, and the destination hosts are unrelated to the package publisher. A second copy of the same dropper is bundled under lib/telemetry.js wrapped as a fake Sentry-like telemetry SDK. The package name mimics a Tinkoff telephony mock but the shipped code is a full-host remote-code-execution dropper against any machine that installs or imports it.

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.