Mozilla Firefox 4.x through 13.0 and Firefox ESR 10.x before 10.0.6 do not have the same context-menu restrictions for data: URLs as for javascript: URLs, which allows remote attackers to conduct cross-site scripting (XSS) attacks via a crafted URL.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.014
EPSS Ranking 79.5%