JavaScript in the "about:webrtc" page is not sanitized properly being assigned to "innerHTML". Data on this page is supplied by WebRTC usage and is not under third-party control, making this difficult to exploit, but the vulnerability could possibly be used for a cross-site scripting (XSS) attack. This vulnerability affects Firefox < 55.
https://www.mozilla.org/security/advisories/mfsa2017-18/
https://bugzilla.mozilla.org/show_bug.cgi?id=1372509