This is a false positive from Windows Defender. The Railway CLI is open source and distributed through npm and GitHub. The Wacac.H!ml detection is a heuristic (machine-learning) signature that commonly flags legitimate CLI binaries. You can safely restore the file from quarantine and add an exclusion for the @railway\cli path in Windows Defender, or install via Scoop as an alternative.

It used to be ok. Windows defender just flags it today. Worth double checking as CLI being hijacked is totally possible.

Your concern is fair. The CLI source is fully auditable at github.com/railwayapp/cli, and published binaries are built from that repo. The Wacac.H!ml signature is a machine-learning heuristic, not a pattern-matched detection, so Windows Defender periodically re-scores binaries and can start flagging a previously-allowed file without anything in the file changing. You can verify integrity by comparing the binary hash against the GitHub release assets.