The COPPA error page in the Accounts setup dialog in Mozilla Firefox OS before 2.2 embeds content from an external web server URL into the System process, which allows man-in-the-middle attackers to bypass intended access restrictions by spoofing that server.
https://bugzilla.mozilla.org/show_bug.cgi?id=1123433
http://www.securityfocus.com/bid/76255
http://www.mozilla.org/security/announce/2015/mfsa2015-75.html