If you go to the site reporting the exploit, it will tell you if your browser is vulnerable to the attack. Security expert Bruce Schneier reports that this exploit may have been used by the NSA.
http://www.techsupportalert.comFeed%3A+gizmosbest+%28Gizmo%27s+Best-ever+Freeware%29
My > FF38.0.1 reports > Logjam Vulnerability (Experimental) > Your user agent is vulnerable. Upgrade as soon as possible.