What browser does contain \x22 code?

I found this unrecognize browser (disguise as Firefox) in my access.log:

\x22Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Firefox/24.0\x22

Although it seems like Firefox version 24.0, I doubt if it is really Firefox. Does anyone know what browser or might be an app that use this user-agent code?