This policy setting controls whether add-ins for the specified Office 2013 applications must be digitally signed by a trusted ...

This policy setting controls whether add-ins for the specified Office 2013 applications must be digitally signed by a trusted publisher. If you enable this policy setting, the specified Office 2013 applications check the digital signature for each add-in before loading it. If an add-in does not have a digital signature, or if the signature did not come from a trusted publisher, the application disables the add-in and notifies the user. Microsoft provides four certificates for the Office 2013 release, which you can add to the Trusted Publishers list. These certificates must be added to the Trusted Publishers list if you require that all add-ins be signed by a trusted publisher. The Microsoft certificates are named Mscert01.cer, Mscert02.cer, Mscert03.cer, Mscert04.cer, and can be found on the Microsoft Web site. The Office 2013 release 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. The Office 2013 release still reads trusted publisher certificate information from the Office trusted publisher store, but it 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 2013 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. For more information about trusted publishers, see the 2013 Office Resource Kit.If you disable or do not configure this policy setting, Office 2013 applications do not check the digital signature on application add-ins before opening them. If a dangerous add-in is loaded, it could harm users' computers or compromise data security.