With the current bugs (constant re-authentication, no copying username/password, no auto-fill) this extension is useless for me. Due to missing Firefox 57 support of this and other addons I have kept Firefox 54 for now with all auto-updating disabled. For all those in the same boat who want to also revert the LP extension back to a working version, here's the link:
https://addons.mozilla.org/en-US/firefox/addon/lastpass-password-manager/versions/