The backend component in Open-Xchange OX App Suite before 7.6.3-rev36 7.8.x before 7.8.2-rev39 7.8.3 before 7.8.3-rev44 and 7.8.4 before 7.8.4-rev22 allows remote authenticated users to obtain sensitive information about external guest users via vectors related to the \groups\ and \users\ APIs.