InformationThis policy setting controls whether add-ins for this applications must be digitally signed by a trusted publisher. The recommended state for this setting is: Enabled. By default, Office 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.
SolutionTo implement the recommended configuration state, set the following Group Policy setting to Enabled. User Configuration\Administrative Templates\Microsoft PowerPoint 2013\PowerPoint Options\Security\Trust Center\Require That Application Add-ins are Signed by Trusted Publisher Impact: Enabling this setting could cause disruptions for users who rely on add-ins that are not signed by trusted publishers. These users will either have to obtain signed versions of such add-ins or stop using them. Office stores certificates for trusted publishers in the Internet Explorer trusted publisher store. Earlier versions of Office stored trusted publisher certificate information (specifically, the certificate thumbprint) in a special Office trusted publisher store. Office still reads trusted publisher certificate information from the Office trusted publisher store, but does not write information to this store. Therefore, if you created a list of trusted publishers in a previous version of Office and you upgrade to the Office release, your trusted publisher list will still be recognized. However, any trusted publisher certificates that you add to the list will be stored in the Internet Explorer trusted publisher store.