Workspace Members & Guests
Any full member of your workspace can access data that is not marked as private. Guests can access data in projects that they have been explicitly added to and that are not marked as private. Learn more about project privacy here, and about how to check who is in your workspace here. 

The Asana Team
Asana team members are bound by confidentiality agreements but may access your data to the extent necessary to diagnose and correct problems in the product. Please read "How Secure is Asana?" for more info.