If you are a screen reader user and also a user of the Mozilla Firefox web browser, please pay close attention to the following information. Do not update to the soon-to-be-released Firefox 57. This upgrade represents such a significant technical and performance change that it’s going to be known as Firefox Quantum. The changes in Firefox Quantum are designed to improve the speed and security of the browser. This, unfortunately, also impacts on the user experience for screen reader users, most screen access software is completely incompatible with Firefox Quantum and those that still function will exhibit a serious deterioration in performance. At this stage, the National Federation of the Blind access technology team, VFO, and NV Access are all recommending that users switch to using Firefox’s Extended Support Release (ESR) version in order to have the latest browser security features and to avoid 57 until it is suitable for use with screen readers.

You can download Firefox ESR here.

Freedom Scientific Statement on Firefox Quantum
NV Access statement on Firefox Quantum