It has been reported that WebCalendar may be prone to multiple SQL injection issues in the view_t.php, view_w.php, view_v.php, and login.php modules of the software. The problems arise from a lack of sufficient sanitization of user-supplied input before being included in database queries.
Successful exploitation of these vulnerabilities may allow a remote attacker to gain access to sensitive information stored in the underlying database. This information may then be used to launch further attacks against a vulnerable system.
http://www.example.com/webcalendar/view_m.php?id=additional sql command