If the device page lists your firmware as version "2.3.1" then that is what you have. To explain, Kobo has pared down the release notes to only list new "enhancements" and as such if (when) they issue a bug fix for a newly generated issue notes aren't necessarily updated. It is a bit of a shame because lots of us would really like to know what they changed, fixed (or broke) but listing all that could take up a good deal of space.
