Code:

https://bugs.chromium.org/p/project-zero/issues/detail?id=1524

uTorrent 3.0-3.5.1 will not be supported anymore due to the vulnerability found in the link above.
This vulnerability allows remote code execution (if you opened Web UI), or download everything you downloaded from you (if you didn't open Web UI)
Nothing except stop using it could prevent an attacker from using it.
We suggest users take uT 2.2.1 or qBittorrent/Transmisstion instead.

For uT 1.8.5-2.2.1, part of the features which contains the vulnerability exists. So we may remove the support of them in the future, if it turns out an attacker could use the vulnerability in another way in 1.8.5-2.2.1.
uTorrent 3.5.3 is a failed patch version, and the staff are waiting for a new stable version which fully fixes the vulnerability. Once found, we shall add support to it.

Please notice that, if you are using uT 1.8.5-2.2.1 currently:
1. Please turn off Web UI
2. Please turn off net.discoverable in advanced setting. This was set to true by default.