qBittorrent official forums

As of today, Windows Defender is flagging qBittorrent as a PUA as seen in the screenshot below.
The "Actions" drop-down only shows "Remove" and "Quarantine" as options. To get it to run, I had to uninstall the application, download the installer, scan the installer with Windows Defender, and specifically allow the application to run on my device.

Known issue sadly. Didn't happen on any computer I manage/use but a friend had this on his PC. He simply downloaded it today again - and Defender no longer flagged it PUA. Probably there was a silent update or something.