How we can reproduce it
(Note: you need to have project which uses Multiplayer, and "Live Mode" should be enabled for your organization)
1 Open https://developer.cloud.unity3d.com/projects/ web site and open your any project that uses Multiplayer
2 Go to Multiplayer->Live Mode tab and enter some not allowed value e.g. 0 for "Global CCU limit" - notice that "Save Changes" button is disabled and you can't press it by mouse (please see image in comment)
3 Press "Enter" on the keyboard

Actual result: Pressing "Enter" on the keyboard is triggering press of disabled "Save Changes" button and page start processing "wrong" value in the "Global CCU limit" field (please see image in comment)

Expected result: Pressing "Enter" on the keyboard should do nothing on the web site for this page