qBittorrent before 5.0.1 proceeds with use of https URLs even after certificate validation errors.

All versions of the qBittorrent client through 4.5.5 use default credentials when the web user interface is enabled. The administrator is not forced to change the default credentials. As of 4.5.5, this issue has not been fixed. A remote attacker can use the default credentials to authenticate and execute arbitrary operating system commands using the "external program" feature in the web user interface. This was reportedly exploited in the wild in March 2023.

In qBittorrent before 4.1.7, the function Application::runExternalProgram() located in app/application.cpp allows command injection via shell metacharacters in the torrent name parameter or current tracker parameter, as demonstrated by remote command execution via a crafted name within an RSS feed.

The UI Lock feature in qBittorrent version 3.3.15 is vulnerable to Authentication Bypass, which allows Attack to gain unauthorized access to qBittorrent functions by tampering the affected flag value of the config file at the C:\Users\<username>\Roaming\qBittorrent pathname. The attacker must change the value of the "locked" attribute to "false" within the "Locking" stanza. NOTE: This is an intended behavior. See https://github.com/qbittorrent/qBittorrent/wiki/I-forgot-my-UI-lock-password

WebUI in qBittorrent before 3.3.11 did not escape many values, which could potentially lead to XSS.

WebUI in qBittorrent before 3.3.11 did not set the X-Frame-Options header, which could potentially lead to clickjacking.