I believe it would be a good idea to re-color the Master password field on the locked extension screen in a red tone/hue, to help distinguish this form from the Search vault field under Tab - at first glace, these two fields are very similar. When I’m working quickly, I often accidentally type my master password into the Search vault field, exposing my master password or parts of it on my screen.
This applies to desktop browser extensions of at least Safari and Chrome.