merge r6909 from branch 2.1 to trunk

bug 1850 fixed: strong check of $_GET['cat']



git-svn-id: http://piwigo.org/svn/trunk@6910 68402e56-0260-453c-a942-63ccdbb3a9ee

comments.php

@@ -104,6 +104,8 @@ $page['where_clauses'] = array();
 // which category to filter on ?
 if (isset($_GET['cat']) and 0 != $_GET['cat'])
 {
+  check_input_parameter('cat', $_GET, false, PATTERN_ID);
+  
   $page['where_clauses'][] =
     'category_id IN ('.implode(',', get_subcat_ids(array($_GET['cat']))).')';
 }