Malicious websites often try to confuse or trick users into giving a site permission to perform an action allowing the site to take control of the users' computers in some manner. Disabling or not configuring this setting allows unknown websites to:
-Create browser windows appearing to be from the local operating system.
-Draw active windows displaying outside of the viewable areas of the screen capturing keyboard input.
-Overlay parent windows with their own browser windows to hide important system information, choices or prompts.
Set the policy value for Computer Configuration -> Administrative Templates -> Microsoft Office 2013 (Machine) -> Security Settings -> IE Security 'Scripted Window Security Restrictions' to 'Enabled' and 'outlook.exe' is checked.
The following resource is also helpful.
This security hardening control applies to the following category of controls within NIST 800-53: System and Communications Protection.This control applies to the following type of system Windows.