Service worker causing CORS issues on Firefox

I'm using service worker for push notifications, following this article. Everything is working with Chrome but with Firefox (v.44.0.2) I have a weird issue. On successful login to my app, I register the service worker which does nothing but waiting for push events; I see that is correctly registered (from some logging and from about:serviceworkers). Now, if I refresh the page (CTRL+R) all my POST have CORS issues (missing Access-Control-Allow-Origin header) due to this service worker and the user is redirected to login page; from here on all POSTs do not work for the same reason. Conversely, if I login, unregister the service worker and then refresh, there are no problems at all. Any idea of what's going on? Again my service worker just handles push events, no caching no other processing done and it perfectly works on Chrome.

Here's my service worker code ( SOME_API_URL points to a real API which is not needed for testing purpose cause the issue happens after the service worker registers, no push events needed)

self.addEventListener('push', function(event) {
  // Since there is no payload data with the first version
  // of push messages, we'll grab some data from
  // an API and use it to populate a notification
  event.waitUntil(
    fetch(SOME_API_URL).then(function(response) {
      if (response.status !== 200) {
        // Either show a message to the user explaining the error
        // or enter a generic message and handle the
        // onnotificationclick event to direct the user to a web page
        console.log('Looks like there was a problem. Status Code: ' + response.status);
        throw new Error();
      }

      // Examine the text in the response
      return response.json().then(function(data) {
        if (data.error || !data.notification) {
          console.error('The API returned an error.', data.error);
          throw new Error();
        }

        var title = data.notification.title;
        var message = data.notification.message;
        var icon = data.notification.icon;
        var notificationTag = data.notification.tag;

        return self.registration.showNotification(title, {
          body: message,
          icon: icon,
          tag: notificationTag
        });
      });
    }).catch(function(err) {
      console.error('Unable to retrieve data', err);

      var title = 'An error occurred';
      var message = 'We were unable to get the information for this push message';

      var notificationTag = 'notification-error';
      return self.registration.showNotification(title, {
        body: message,
        tag: notificationTag
      });
    })
  );
});

self.addEventListener('notificationclick', function(event) {
  console.log('On notification click: ', event.notification.tag);
  // Android doesn't close the notification when you click on it
  // See: http://crbug.com/463146
  event.notification.close();

  // This looks to see if the current is already open and
  // focuses if it is
  event.waitUntil(
    clients.matchAll({
        type: 'window'
      })
      .then(function(clientList) {
        for (var i = 0; i < clientList.length; i++) {
          var client = clientList[i];
          if (client.url == '/' && 'focus' in client)
            return client.focus();
        }
        if (clients.openWindow) {
          return clients.openWindow('/');
        }
      })
  );
});

Firefox 44 has bug 1243453, which causes the Origin header of cross-origin requests to get dropped if the service worker doesn't listen for fetch events.

The bug has been fixed in Firefox 45, which will be released the week of March 8, 2016 (next week, as of the time of this writing). In the meantime, and for users who don't immediately upgrade to the latest Firefox release, you can work around the problem by adding this code to the service worker:

addEventListener('fetch', function(evt) {
  evt.respondWith(fetch(evt.request));
});