UPDATE: LastPass support told me in a ticket that they are abandoning the LastPass addon after Firefox version 56. It will no longer be supported. Further more they recommended using Google Chrome instead of Firefox. That's loyalty for you...

Original: Before Firefox 57 on Android the LastPass addon worked well. Now you cannot login to your LastPass account with the addon. I opened a ticket with LastPass support (since I'm a paying premium member) only to be told this is a known problem with the addon since the release of Firefox 57 and that there is no ETA on a fix planned anytime soon.