ARS Technica writes the threat level is pretty high as malicious websites could abuse the security bug to run arbitrary code on your PC:
The vulnerabilities, according to Project Zero, make it possible for any website a user visits to control key functions in both the uTorrent desktop app for Windows and in uTorrent Web, an alternative to desktop BitTorrent apps that uses a Web interface and is controlled by a browser. The biggest threat is posed by malicious sites that could exploit the flaw to download malicious code into the Windows startup folder, where it will be automatically run the next time the computer boots up. Any site a user visits can also access downloaded files and browse download histories.Users of uTorrent need to upgrade to version 3.5.3.44352. Web users of uTorrent need to ensure they're running build 0.12.0.502 to be protected.