Index: lib/filterListener.js
===================================================================
--- a/lib/filterListener.js
+++ b/lib/filterListener.js
@@ -137,20 +137,18 @@
  */
 function addFilter(filter)
 {
   if (!(filter instanceof ActiveFilter) || filter.disabled)
     return;
 
   let hasEnabled = false;
   let allowSnippets = false;
-  for (let i = 0; i < filter.subscriptions.length; i++)
+  for (let subscription of filter.subscriptions)
   {
-    let subscription = filter.subscriptions[i];
-
     if (!subscription.disabled)
     {
       hasEnabled = true;
 
       // Allow snippets to be executed only by the circumvention lists or the
       // user's own filters.
       if (subscription.type == "circumvention" ||
           subscription instanceof SpecialSubscription)
@@ -184,19 +182,19 @@
 function removeFilter(filter)
 {
   if (!(filter instanceof ActiveFilter))
     return;
 
   if (!filter.disabled)
   {
     let hasEnabled = false;
-    for (let i = 0; i < filter.subscriptions.length; i++)
+    for (let subscription of filter.subscriptions)
     {
-      if (!filter.subscriptions[i].disabled)
+      if (!subscription.disabled)
       {
         hasEnabled = true;
         break;
       }
     }
     if (hasEnabled)
       return;
   }