feature: only try sending events if the origins match

content/install-hook-openusercss.js

@@ -7,24 +7,26 @@
     'https://openusercss.com'
   ];
 
+  const sendPostMessage = message => {
+    allowedOrigins.forEach(origin => {
+      if (origin === location.origin) {
+        window.postMessage(message, origin);
+      }
+    });
+  };
+
   const askHandshake = () => {
     // Tell the page that we exist and that it should send the handshake
-    allowedOrigins.forEach(origin => {
-      window.postMessage({
+    sendPostMessage({
       type: 'ouc-begin-handshake'
-      }, origin);
     });
   };
 
   // Listen for queries by the site and respond with a callback object
   const sendInstalledCallback = styleData => {
-    allowedOrigins.forEach(origin => {
-      if (origin === location.origin) {
-        window.postMessage({
+    sendPostMessage({
       type: 'ouc-is-installed-response',
       style: styleData
-        }, origin);
-      }
     });
   };
 
@@ -90,15 +92,13 @@
 
     // We send the handshake response, which includes the key we got, plus some
     // additional metadata
-    allowedOrigins.forEach(origin => {
-      window.postMessage({
+    sendPostMessage({
       type: 'ouc-handshake-response',
       key: event.data.key,
       extension: {
         name: manifest.name,
         capabilities: reportedFeatures
       }
-      }, origin);
     });
   };
 
@@ -118,11 +118,9 @@
   const sendInstallCallback = data => {
     // Send an install callback to the site in order to let it know
     // we were able to install the theme and it may display a success message
-    allowedOrigins.forEach(origin => {
-      window.postMessage({
+    sendPostMessage({
       type: 'ouc-install-callback',
       key: data.key
-      }, origin);
     });
   };