Exception site list box in Java Control Panel is greyed out thus disallowing addition of an item to the exception list.
This is reproducible always on a Windows 7 (64-bit) system with JRE 8u60 and 9 ea b78. For 8u51, the behavior and display is normal.

Checked this on another Windows 7 (64-bit), system and the display and behavior is fine.

Attached screenshots depicting thie behavior (for 8u51 and 8u60).