MAL-2026-12866 Malicious code in bnpl-blocks-atom-bnpl-breadcrumbs (npm)

On require() of the package, index.js loads polyfill.js, which fetches a platform-specific opaque binary from obfuscated Cloudflare Workers subdomains (oob-worker.cf100-.workers.dev, oob-worker.cf101-.workers.dev, etc.) and, if HTTPS delivery fails, falls back to reassembling the payload from base64-encoded DNS TXT records under *.dl.wel1.ru (query c.<domain> for a chunk count, then concatenate N.<domain> TXT records). The retrieved bytes are written to /var/tmp or %TEMP% under a disguised filename (.cache<hex> on POSIX, dotnet_diag_<hex>.exe on Windows), chmod 0755'd, and detach-spawned via /bin/sh -c "<file> &" or cmd /c start, with.unref() so the process outlives the require() call. C2 hostnames are assembled at runtime by array-join splits (["oob-","worker.cf10","0-416.w","orkers.d","ev"].join(""), ['sdk.dl.wel1','.ru'].join("")) to defeat static string scanning, and the code respects DO_NOT_TRACK/DISABLE_TELEMETRY environment variables as a review-evasion gate. The staged filenames impersonate legitimate diagnostic tooling and a hidden marker file (.analytics_state) is used to track prior execution. No verification (hash, signature, pinning) is performed on the fetched binary.

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.