PHP 5.6.16
RoundCube 1.1.4
If I log in with username "dennis" I can perform the login. In the table "users" is now a entry with "dennis" as username available. That's correct!
If I log in with username "Dennis", roundcube creates a new user in the table "users" and all my settings are lost (signatures, identities etc.)
Now I can login with different large and lower case users (e.g. dEnnis, deNnis, denNis, DenNiS...) and create different entries for the same user!