MDL-20901 fixed input validation

calendar/preferences.html

@@ -83,6 +83,7 @@
 
 <tr>
     <td colspan="2" style="text-align: center;">
+    <input type="hidden" name="sesskey" value="<?php echo sesskey(); ?>" />
     <input type="submit" value="<?php print_string("savechanges") ?>" /></td>
 </tr>
 </table>

calendar/preferences.php

@@ -21,7 +21,7 @@ calendar_session_vars();
 
 /// If data submitted, then process and store.
 
-if ($form = data_submitted()) {
+if ($form = data_submitted() and confirm_sesskey()) {
     foreach ($form as $preference => $value) {
         switch ($preference) {
             case 'timeformat':