Firefox requests it to allow websites to create audio and visual applications using a technology called WebRTC. The most common use of WebRTC is used to create video chat websites between two or more users, https://appear.in/ is an example of this usage. Granting this access is a two part process. The first step is that Firefox would need the user to approve the Android level permissions. The second step is that each website that wants to use the camera or microphone must ask the user to gain access each time the camera or microphone is accessed. Firefox never records audio, takes pictures or records video unless you opt-in each time the website asks. https://support.mozilla.org/en-US/kb/how-firefox-android-use-permissions-it-requests