Seems that the settings are not saved Rated 1 out of 5 stars

The plugin has become unusable as the Firefox address bar now only shows one from the history/bookmarks and then the rest are from Instafox. The behaviour does not change even after adjusting the settings.

This review is for a previous version of the add-on (2.7.9.1-signed).  This user has a previous review of this add-on.

Juahan, thank you very much for your bugreport, we just fixed it! I hope this helps, please let me know! :)
https://addons.mozilla.org/en-US/firefox/addon/instantfox/versions/#version-2.8.2 (currently in Mozilla review)