A good start, but to be complete, it must works in off-line mode and automatically catch-and-save login form.

Multiple accounts don't work - the vault from the 'first' account is always shown. The vault belonging to the second account doesn't appear.
Even after I deleted all accounts from the add-on, the vault is still shown with all its passwords, so credentials for the vault are cached in some way. This is the security flaw.
So far the very basic functionality is usable, only with a single account.

Setup process is too complicated, requires several passwords cloud+vault+extension and you cannot copy/paste them in because as soon as you click off it, it closes and starts again which sucks because my passwords are long and high-entropy so are awkward to type in manually.
When sites have multiple matches, copying the right password requires multiple clicks to "edit" the entry, there is no simple right-click context menu, and no auto-fill option either making it much slower to use than Lastpass.
Besides poor UI/UX design it has worked fine since installed, I'll keep an eye on it but cannot commit to it yet.

I had to rank it a three, because I could find no way to login to my Nextcloud instance on Android's Firefox. This is my final step to being rid of third party pass managment! I hope they fix this soon!