App including secure service with attachments asking to login twice

[RussellCamp]

I have a web app, with a secure service that has photo attachments. when the app loads, ArcGIS Online asks for authentication, then when the user tries to access a photo attachment, ArcGIS Server Rest API asks to authenticate a second time. How do I eliminate the need for the second login request and just open the attachment?

[RussellCamp · Accepted solution]

I figured it out, you have to configure trusted servers in ArcGIS Online and add your server to the trusted list.

[DavidColey]

Hi Russell - can you verify that you are using Web Tier authentication, this doesn't affect GIS Tier / token authentication