If you are a Linux users, you know what /etc/passwd, .ssh keyfiles or FileZilla site konfiguration files are, and how weird it could be if these files are stolen.
If you are a Windows users, imagine what could happen if your keyword files are stolen.
So, please, update your Firefox browser to Firefox 39.0.3 or to Firefox ESR 38.1.1
A nice exploit has recently been discovered, which makes urgent to update to the current level.
Have a look at the Mozilla blog, right here :
https://blog.mozilla.org/security/2015/08/06/firefox-exploit-found-in-the-wild/
Of course, this exploit has been detected in very particular conditions, there is probably no reason to catch it in your computer. However, updating is such an easy process that there is no reaseon not to perform it right now.
Regards
Yordan