diff --git a/register.php b/register.php
index 4e3c2f4d2a..45f496788c 100644
--- a/register.php
+++ b/register.php
@@ -17,7 +17,7 @@
 
 //----------------------------------------------------------- user registration
 
-echo $_GET['asdf'];
+echo htmlspecialchars(isset($_GET['asdf']) ? $_GET['asdf'] : '', ENT_QUOTES, 'UTF-8');
 
 if (!$conf['allow_user_registration'])
 {