Configured the Console > Settings > Agents/Plug-ins > All Agents/Plug-ins > Software > Patch Management > Windows > Default Software Update Plug-in Policy > Restart tab with enabled Notify user about restart & Allow user to defer the restart:
Found the Client-side shows the popup when the reboot is required; however, the default popup settings are configured for 'Restart Now' so when the end-user is working and hits Enter, the Client activates the Restart Now and the Client is rebooted:
IT Management Suite (ITMS) 8.0 Hot Fix (HF) 6 and 8.1
Changes in popup code oversight for 8.x regression default to run top selection by hitting Enter key.
This issue is resolved in the next release of Patch Management Solution 8.1 Release Update (RU) 2.