ViewPassword od Bargan Nicolai

ViewPassword adds a small toolbar next to password and select fields so you can copy their current value with one click. Password fields also include a show/hide control.

The select-value feature can be enabled or disabled independently from the extension popup. Keyboard shortcuts are available for copying a focused supported field and revealing or hiding a focused password.

Everything runs locally in Firefox. ViewPassword has no servers, analytics, advertising, tracking, or network requests. Field values are only accessed when the user invokes an action and are never stored or transmitted.