Impact

A brute force exploit that can be used to collect valid usernames is possible.

Explanation of the vulnerability

It's a brute force exploit that can be used to collect valid usernames by using the “forgot password” function when trying to log into the Backoffice.
If the username/email is known, it is easier to find the corresponding password.
If an email address that was already used and registered by a user, is provided as an input, the server internal processing time takes longer.
If the email address does not exist in the database of the registered users, the server would respond immediately.