This site temporarily prohibits the use of qBittorent v4.5 and above
The Windows version of qBittorent v4.5.1 reported a vulnerability when using the web client. A remote attacker could use this vulnerability to browse files on the system.

v4.5.0 is also temporarily disabled.
Versions v4.4.5 and earlier are not affected by this bug.


The bug is described here.
https://github.com/qbittorrent/qBittorrent/issues/18618
If you are using the Windows version of qBittorrent v4.5.1, roll back to v4.4.5 or earlier. If you've never enabled the webUI, you should be fine as it's off by default.