With Power BI, you can use an app built by a company or individual other than Microsoft. For example, you might use a third party app which integrates Power BI tiles into a custom built web application. When you use a third party app, you will be asked to grant that application certain permissions to your Power BI account and resources. It is important that you only grant permissions to applications that you know and trust. Permissions to an application can be revoked at any time. See Revoke third party app permissions.
Here are the types of access an application can request.
View all Dashboards
View all Reports
View all Datasets
Read and Write all Datasets
View user's Groups
You revoke permissions for a third party app by going to the Office 365 My Apps site.
On the Office 365 My apps site, here's how to revoke third party permissions: