This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Mozilla Firefox. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file. The specific flaw exists within the handling of HTML5 end tags. The issue lies in the failure to check for an index becoming negative, allowing for out-of-bounds indexing. An attacker can leverage this vulnerability to execute code within the context of the current process.