We are looking at enabling a feature that focuses on supporting CORS preflight requests between two applications. This works by allowing you to configure the response and have App Proxy handle it on behalf of the app.
A pre-requisite for this feature to work is that the user must be able to authenticate into the second application in order to avoid a CORS issue from the login flow into the second app.
To avoid this the user will have to make sure they have already accessed the 2nd application before the CORS request, and has valid credentials. This should work for wildcard apps and can also be achieved by adding a fake link / image to the 2nd application in the first application.
We would love to get your feedback on this requirement and if this is something that will fit your use case.
An error occurred while saving the commentJohn Atwood commented
You can work around this limitation by using an Azure Function Proxy to proxy your App Proxy App and set CORS allowed origins: