Since recently (90+ versions) I've noticed that [https://addons.mozilla.org/en-US/firefox/addon/nighttab/ nightTab] seemingly randomly resets itself to default settings which wasn't caused by browser wide cookies and data reset. After poking a bit, I've found a consistent way to reproduce this issue: # Visit any site which stores cookies # Clear data and cookies on that site # Open new tab and have nighttab reset Besides clearing out extension cookie, some websites also partially reset their settings, but not login information.