DTOO200 - Office must be configured to not allow read with browsers.
The Windows Rights Management Add-on for Internet Explorer provides a way for users who do not use the 2013 Office release to view, but not alter, files with restricted permissions. By default, IRM-enabled files are saved in a format that cannot be viewed by using the Windows Rights Management Add-on. If this setting is enabled, an embedded rights-managed HTML version of the content is saved with each IRM-enabled file, which can be viewed in Internet Explorer using the add-on, representing the risk of documents being read by those without the rights and not intended to have access to the document.
Set the policy value for User Configuration -> Administrative Templates -> Microsoft Office 2013 -> Manage Restricted Permissions 'Allow users with earlier versions of Office to read with browsers' to 'Disabled'.