Flask registration

Introduction

Flask-Login provides user session management for Flask . It handles the common tasks of logging in, logging out, and remembering your users’ sessions over extended periods of time. It will: Store the active user’s ID in the session, and let you log them in and out easily.

the login process seems secure . But you didn’t check the potential existing user in the signup form, or existing email address. Unless this is managed by the underlying User schema. And you should require a minimal password complexity.