Yes, If I'm not click any other windows, it will show at the top of setup window.
But if I click other windows when it is in the setup process, it will appear this issue.
I actually wanted to tell you about this a long time ago.
When I was a starter to use Maxthon 6.
That time, when the installation, in 86% stay for more than ten minutes, I have no idea what is the situation. I didn't get any hints.
Finally, I minimized all the Windows and found this UAC window.
And this issue can reproduced in the latest build.