I found this post on another torrent site
The report does look credible. I have not investigated it in detail so I can't say if I agree with it. I suggest that you follow the link and make up your own mind.
If you are not sure what to do then upgrade to the latest version.
Code:
Due to a vulnerability in the WebUI of qBittorrent v4.5.0 and v4.5.1, all users of those two versions should update to v4.5.2 as soon as possible.
The flaw was reported here:
https://github.com/qbittorrent/qBittorrent/issues/18618
Short version: it allows arbitrary files to be read remotely.
We still recommend version v4.3.9 as the most stable, and discourage anything older than v4.3.4 due to it not checking ssl certificates (leaving it open to MITM and similar attacks)"
The report does look credible. I have not investigated it in detail so I can't say if I agree with it. I suggest that you follow the link and make up your own mind.
If you are not sure what to do then upgrade to the latest version.