I applied this fix myself yesterday and so far, no more popups. Then, in the File Download dialog box, click Run or Open, and follow the steps in the fix wizard.'
In the meantime, customers can turn off the notification by first clicking here. The team is actively working to identify the right frequency and are also evaluating ways to make adjusting the notification simple based on customer feedback. A spokesperson provided the following statement: 'The notification is meant to provide existing Office 365 subscribers who are using an older version of Office an easy way to upgrade to Office 2016.