Have you tried this add-on?

• https://addons.mozilla.org/en-US/firefox/addon/saved-password-editor/

If you want to delete it and let Firefox save it again on the next visit, you should be able to do that here:

orange Firefox button (or Tools menu) > Options > Security > "Saved Passwords"

Note that your System Details List shows that you have a user.js file in the profile folder to initialize some prefs on each start of Firefox with a possible feed.snapdo.com infection.

The user.js file is only present if you or other software has created it, so normally it wouldn't be there. You should check its content with a plain text editor if you didn't create this file yourself.

The user.js file is read each time you start Firefox and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.

• http://kb.mozillazine.org/Preferences_not_saved