After upgrading php to version 5.6 with all related packages such as apache, I cannot log into my 
mail account anymore (I am running my own e-mail test server on a virtualbox) 

I think I am honing in on the problem:
I upgraded everything from mageia4 to mageia5 but not:
roundcubemail
php
apache

and I do not have problem to login. After updating php (with all php related packages) and apache, I 
get the following error in journalctl  httpd.service

Jan 14 17:59:41 vbox.btspuhler.com suhosin[4907]: ALERT - ASCII-NUL chars not allowed within request 
variables - dropped variable '_url' (attacker '127.0.0.1', file '/usr/share/roundcubemail/index.php')
Jan 14 17:59:41 vbox.btspuhler.com suhosin[4907]: ALERT - dropped 1 request variables - (0 in GET, 1 
in POST, 0 in COOKIE) (attacker '127.0.0.1', file '/usr/share/roundcubemail/index.php')

Has anybody else experienced this? 