Word 2 and earlier binary documents and templates must be blocked for open/save.

This setting specifies whether users can open, view, edit, or save Word files saved in the specified format. Enabling block of the specified format mitigates zero-day security attacks (which are attacks that occur during between the time that a vulnerability becomes publicly known and a software update or service pack is available) by temporarily preventing users from opening specific types of files and to prevent a user from opening files that have been saved in earlier and pre-release (beta) Microsoft Office formats.