Uncheck Stay signed in Yahoo Login от backy0175

This addon uncheck "Stay signed in" automatically.

Supports option "Hide Stay signed in" for public PC.

Maybe my other addon "Uncheck Stay-signed-in for Google Login" will help you.
https://addons.mozilla.org/firefox/addon/uncheck-stay-signed-in/


Important Information: 2016/03/16
Mozilla is changing a lot of things about add-on development again. So this addon might be stop working in the future.

"The Future of Developing Firefox Add-ons | Mozilla Add-ons Blog"
https://blog.mozilla.org/addons/2015/08/21/the-future-of-developing-firefox-add-ons/

"Add-ons/developer/communication - MozillaWiki - Upcoming Changes in Add-on Development"https://wiki.mozilla.org/Add-ons/developer/communication#Upcoming_Changes_in_Add-on_Development