CVE 2016-2831
Mozilla Firefox before 47.0 and Firefox ESR 45.x before 45.2 do not ensure that the user approves the fullscreen and pointerlock settings, which allows remote attackers to cause a denial of service (UI outage), or conduct clickjacking or spoofing attacks, via a crafted web site.
See the 
CVE page on Mitre.org
for more details.
