add listenForExternalMessages option

src/wrap-store/wrapStore.js

@@ -62,10 +62,14 @@ const defaultOpts = {
  * Wraps a Redux store so that proxy stores can connect to it. This function
  * must be called synchronously when the extension loads to avoid dropping
  * messages that woke the service worker.
+ * @param {boolean} options.listenForExternalMessages Controls if other
+ * extensions can access the store via onMessageExternal (default is false). Use
+ * with caution, this allows any other extension to read the store and dispatch
+ * actions.
  * @return {WrapStore} The wrapStore function that accepts a Redux store and
  * options. See {@link WrapStore}.
  */
-export default () => {
+export default ({ listenForExternalMessages } = {}) => {
   const browserAPI = getBrowserAPI();
 
   // Setup message listeners synchronously to avoid dropping messages if the
@@ -76,10 +80,16 @@ export default () => {
   browserAPI.runtime.onMessage.addListener(stateProviderListener.listener);
   browserAPI.runtime.onMessage.addListener(actionListener.listener);
 
-  if (browserAPI.runtime.onMessageExternal) {
-    browserAPI.runtime.onMessageExternal.addListener(actionListener.listener);
-  } else {
-    console.warn("runtime.onMessageExternal is not supported");
+  if (listenForExternalMessages) {
+    if (browserAPI.runtime.onMessageExternal) {
+      // Listen for messages from other extensions
+      browserAPI.runtime.onMessageExternal.addListener(
+        stateProviderListener.listener
+      );
+      browserAPI.runtime.onMessageExternal.addListener(actionListener.listener);
+    } else {
+      console.warn("runtime.onMessageExternal is not supported");
+    }
   }
 
   return (