I noticed an odd issue with the Contao demo. If you try to log into the back end via http://demo.contao.org/contao/login (so no https), it just redirects you to the front end.
That was most likely a problem with the server configuration. You should not have been able to access the installation via HTTP at all. I have fixed this now.
I noticed an odd issue with the Contao demo. If you try to log into the back end via http://demo.contao.org/contao/login (so no https), it just redirects you to the front end.
Logging in via https works fine.