All of these top comments remind me of the general adage that encryption and security are really hard, and if you think you know what you're doing you probably don't.

I don't want to be too harsh for a ShowHN, but even if the authors fixed the several bugs that have already been reported here, it's clear they don't have a foundational enough understanding of cryptography and security to be writing a password manager. I would suggest they spend more time understanding the basics first.