Vikunja before 2.7.1 Information Disclosure via Team Self-Removal Endpoint

Vikunja before 2.7.1 contains an information disclosure vulnerability that allows authenticated users to determine whether private teams exist by calling the team member self-removal endpoint. Attackers can send DELETE requests to /teams/{id}/members/{own username} for arbitrary team ids and use the distinguishable responses to learn if a team exists, is SSO-managed, or has a single member.