Office 2013 applications do not check the digital signature on application add-ins before opening them. Disabling or not configuring this setting may allow an application to load a dangerous add-in. As a result, malicious code could become active on user computers or the network.
Set the policy value for User Configuration -> Administrative Templates -> Microsoft InfoPath 2013 -> Security -> Trust Center 'Require that application add-ins are signed by Trusted Publisher' to 'Enabled'.
The following resource is also helpful.
This security hardening control applies to the following category of controls within NIST 800-53: Configuration Management.This control applies to the following type of system Windows.