Quassel core (server daemon) in Quassel IRC before 0.9.2 does not properly verify the user ID when accessing user backlogs, which allows remote authenticated users to read other users' backlogs via the bufferid in (1) 16/select_buffer_by_id.sql, (2) 16/select_buffer_by_id.sql, and (3) 16/select_buffer_by_id.sql in core/SQL/PostgreSQL/.