JeecgBoot through 3.9.5 contains an insecure direct object reference vulnerability that allows authenticated users to read other users' in-application messages via the getOne handler of SysAnnouncementSendController. Attackers can obtain delivery record ids from the unguarded /sys/sysAnnouncementSend/list endpoint and supply them as the sendId parameter to retrieve message titles, bodies, senders and recipients.