[WeChall] Are you serial

We are serialsly trying to build a secure website.
This time, we have it secure and extensible, and of course you can see all the sourcecode again:

code.php
insecure.inc.php
SERIAL_LoginForm.php
SERIAL_LogoutForm.php
SERIAL_Solution.php
SERIAL_User.php

As always, code you see is code in use.

GeSHi`ed PHP code for insecure.inc.php

<?php
/**
 * Ultra Safe Auto Include
 * @author Z
 * @param string $classname */
function my_autoloader($classname)
{
        chdir('challenge/are_you_serial');
        require_once './'.str_replace('.', '', $classname).'.php';        chdir('../../');
}
 
/**
 * Registers auto include */
spl_autoload_register('my_autoloader');
?>