You are able to connect specific Xero and QBO organizations to specific Excel workbooks.  When the workbook is saved and shared, the workbook will open with only those saved organizations.
Here is a short video showing the security enhancement and how-to for sharing the workbook.
When you save, close, and reopen the workbook,  the previously selected organizations will be maintained.  So, when you subsequently share the workbook with a colleague or client, they will only be able to access data from the selected orgs.
If you do not wish your client or colleague to be able to recalc the workbook, use the add-in, and only see values,  you will need to disconnect the orgs (Organization tab) from the workbook, protect the workbook in Excel, save the workbook, then share it.