Will Google Commerce Search allow Google or anyone else to access my site's secure data?
Google Commerce Search was designed with security in mind; your search engine only provides search results for public content that is already available for indexing on Google.com. If your secure website content is password-protected, it is not available for anyone else to access through Google.com or your search engine.
Google Commerce search places products you uploaded into Google Shopping where users can view those items publicly. You can, however, specify certain custom attributes for your products visible only to you.