Index: modules/system/system.admin.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.admin.inc,v
retrieving revision 1.292
diff -u -p -r1.292 system.admin.inc
--- modules/system/system.admin.inc	8 Jul 2010 03:41:27 -0000	1.292
+++ modules/system/system.admin.inc	26 Jul 2010 12:43:32 -0000
@@ -672,8 +672,10 @@ function system_theme_settings_validate(
     }
   }
 
+  $validators = array('file_validate_extensions' => array('ico	png gif jpg jpeg apng svg'));
+
   // Check for a new uploaded favicon.
-  $file = file_save_upload('favicon_upload');
+  $file = file_save_upload('favicon_upload', $validators);
   if (isset($file)) {
     // File upload was attempted.
     if ($file) {