When you go to the kproxy add-on page you'll see a small text line under "+Add to Firefox" reading "''This add-on has not been reviewed by Mozilla.''" If you click the read more link it will bring up the following: '''What does it mean if an add-on is "not reviewed"?''' ''While all add-ons publicly available in our gallery are reviewed by an editor, you may receive a direct link to an add-on that hasn't yet been reviewed. Use caution when installing these add-ons, as they could harm your computer or violate your privacy. We recommend that you only install reviewed add-ons.'' To answer your question, the add-on is not "blessed" by Mozilla/Firefox. Therefore it would be best to advise you to be cautious. Add-ons are created by other users and can possibly be malicious.