"WIndows NT 9.0" ? Rated 3 out of 5 stars

IE9 has 'WIndows NT 9.0' in the UA string. Haven't tried any of the other UA's.

This review is for a previous version of the add-on (0.2.2.1-signed). 

You are absolutely right
I was already updating to version 0.3.0, but I corrected the error mentioned by you and I'm releasing version 0.3.1
But this version is awaiting the review of Mozilla, but you can see on 'Version Information' > 'See complete version history'

thanks for the review