It took me a while to find this one and I assume its a bug. The KendoDialog (confirm) fires twice on pressing return instead clicking with the mouse on it. You can try that on your API samples, like here
The link will head you to the actions.action sample.
1. Switch to preview mode of actions.action
2. Press TAB key once to focus the "Ok" button
3. Press the ENTER (RETURN) key
You will see that the message "OK action was clicked" will appear twice (click close on first message then the second message appears).
Clicking on the OK button with the mouse will show the message only once (as it should).
Beside of finding that problem it brings me into certain troubles now because the dialog buttons in my project are associated with server side functions (calling them) and now I have some unwanted side effects/data constellation on my server. :/
I just found this on KendoDialog confirm. I have no idea if that effect can also be found in other Kendo widgets (I hope not).