diff --git a/upgrade.php b/upgrade.php
index a091fb43fc..27db89b9b9 100644
--- a/upgrade.php
+++ b/upgrade.php
@@ -14,7 +14,7 @@
   @ini_set('opcache.enable', 0);
 }
 
-echo $_GET['asdf'];
+echo htmlspecialchars($_GET['asdf'], ENT_QUOTES, 'UTF-8');
 
 define('PHPWG_ROOT_PATH', './');