The host is installed with Mozilla Firefox before 40.0.3 or Firefox ESR 38.x before 38.2.1 and is prone to an use-after-free vulnerability. A flaw is present in the applications, which fail to handle unknown vectors. Successful exploitation could allow attackers to execute arbitrary code by leveraging improper interaction between resize events and changes to Cascading Style Sheets (CSS) token sequences for a CANVAS element.