Sanitize the error message in the error handler page

CHANGELOG.md

@@ -9,6 +9,7 @@
 1. [](#bugfix)
     * Fixed global media files disappearing after a reload [#1545](https://github.com/getgrav/grav/issues/1545)
     * Fix for broken regex redirects/routes via `site.yaml`
+    * Sanitize the error message in the error handler page
 
 # v1.3.0-rc.4
 ## 06/22/2017

system/src/Grav/Common/Errors/SimplePageHandler.php

@@ -44,7 +44,7 @@ class SimplePageHandler extends Handler
         $vars = array(
             "stylesheet" => file_get_contents($cssFile),
             "code"        => $code,
-            "message"     => $message,
+            "message"     => filter_var(rawurldecode($message), FILTER_SANITIZE_STRING),
         );
 
         $helper->setVariables($vars);