qBittorrent official forums

Since last update, Windows Defender is classifying qBittorrent as Potentially unwanted app and blocking its execution.

Detected: PUA:Win32/QBitTorrent

(not saying it is a virus or if the Windows Defender is doing a good or bad job, just letting you guys know this).

The detection is in qbittorrent_4.3.4.1_x64_setupexe->(UPX)->(nsis-6-e) and in qbittorrent.exe

(WDefender didn't blocked or complained about the setup, just blocked the execution... I guess all you need to do to create a virus that pass through WDefender is to make a setup.exe =P)

Thanks for reporting but its known and false. Microsoft Defender is acting weird lately with different clients also.

See 4.3.4 news here: https://www.qbittorrent.org/news.php
It's just Microsoft being Microsoft.