It is impossible to login to Share via the SSO bypass login page (page?pt=login) when external authentication is enabled.
[Steps to reproduce]
1- Enable external authentication on a vanilla 5.0.1 environment
2- Go to http://server:port/share/page?pt=login
3- Log in
You get logged in and see the dashboard.
The URL displayed in the address bar is the dashboard URL, but you still see the login form.
[Analysis to date]
Using a client debugger (e.g FireBug), we can see that the elements of the dashboard are called. Though, the login form is still being displayed (see attached screen_capture_001.jpg).
The issue is not reproduced on 188.8.131.52