Hi Keith,
Thanks for your reply, Is it possible for you to share how did you implement this?
I tried adding this code into the index.php file but doesn't work correctly for the Admin are and do not work at all in the catalog
require_once('/path/to/htmlpurifier/library/HTMLPurifier.auto.php');
$config = HTMLPurifier_Config::createDefault();
$purifier = new HTMLPurifier($config);
// Clean user input in GET array
$_GET = $purifier->purify($_GET);
// Clean user input in POST array
$_POST = $purifier->purify($_POST);
// Clean user input in REQUEST array
$_REQUEST = $purifier->purify($_REQUEST);