To reduce the risk of embedded content being pulled in from unknown sites, Office 365 is setting a default list of sites and domains that are recognized as safe. We are rolling this out today, and the roll out will be completed in the following days.
How does this affect me?
We are updating the default list of sites and domains (found in the HTML Field Security setting) to include additional, commonly used websites from Microsoft and Google services. This will improve the content embedding experience.
What do I need to do to prepare for this change?
There is nothing you need to do to prepare for this change. Please click Additional Information to see the list of sites we are adding, as well as how to change the domains in the HTML Field Security setting list.