I installed Xampp 188.8.131.52 on Ubuntu 14.01 LTS Desktop under Oracle VM.
I followed the guides and after the installation I run the security to change the passwords.
I changed all passwords successfully and I restarted the Xampp server.
However the http://localhost/xampp is still accessible and dont ask for Username and Password.
Going to Security link it says: "These Xampp pages are no longer accessible by network from everyone - SECURE"
MySQL, phpmyadmin and PROFTpd work as expected.