Steps to reproduce: 1. Create a service worker with the following source code: self.onmessage = function(event) { console.log(event.origin); }; 2. Register a new service worker and transmit data to it via the `postMessage` API Expected result: the value of the client's origin (e.g. `location.origin`) should be printed to the developer's console. Actual result: the empty string (`""`) is printed to the developer's console. Operating System: Ubuntu 16.04 (x86_64) Browser: Firefox Nightly Contents of `platform.ini` file: [Build] BuildID=20170316110253 Milestone=55.0a1 SourceRepository=https://hg.mozilla.org/mozilla-central SourceStamp=ff04d410e74b69acfab17ef7e73e7397602d5a68 Reference: https://w3c.github.io/ServiceWorker/#extendablemessage-event-origin > 4.8.2. event.origin > > The `origin` attribute must return the value it was initialized to. When the > object is created, this attribute must be initialized to the empty string. It > represents the origin of the service worker client that sent the message.

I expect this to be fixed as part of my work in bug 1293277.

Note, this was not fixed as part of bug 1293277. Its probably a one line fix to set this properly.