Incorrect Privilege Assignment

Summary

Grav is a file-based Web platform. In versions prior to 1.8.0-beta.27, a Privilege Escalation vulnerability exists in Gravs Admin plugin due to the absence of username uniqueness validation when creating users. A user with the create user permission can create a new account using the same username as an existing administrator account, set a new password/email, and then log in as that administrator. This effectively allows privilege escalation from limited user-manager permissions to full administrator access.