Yahoo! Mail Notifier 18.104.22.168.1-signed.1-let-fixed.1-signed
All personal information is stored locally in the user's browser profile and is not transmitted to any party save Yahoo for the purposes of logging in.
If the user so chooses, the add-on will remember the user's Yahoo password. This is saved in the browser's password manager. If the user chooses to remember his/her Yahoo password, it is recommended that the user specify a master password in the browser to safeguard the password. Warning, it is possible for other add-ons to access your passwords so make sure you only install trusted add-ons.
The add-on stores a copy of one of the user's Yahoo cookies in the browser preference file for purposes of automatically logging the user in to Yahoo Mail. If the user has opted not to store his/her Yahoo password, the copy is wiped when the browser is closed otherwise it is wiped every 12 hours. The cookie data copy cannot be used to gain access to the user's Yahoo account unless the user was already previously logged in as that user.