on facebook.com, mozilla shows for www.facebook.com 0 cookies 2.6 MB local storage and for facebook.com 3 cookies, whereas the plugin shows 0 headers 0 cookies. Hence seems the plugin misses some cases
Well well, I am a developer and used to check headers as per security standard. This plugin helps me to do my work very easily, specilay headers suggestion (It flash message if your header values is wrong).
Millions Thanks to Dev, who took time to build such a wonderful peace of work :)