Permissions, Privileges, and Access Controls
Flat Calendar 1.1 does not properly restrict access to administrative functions, which allows remote attackers to (1) add new events via calAdd.php, as reachable from admin/add.php, or (2) delete events via admin/deleteEvent.php. NOTE: this is only a vulnerability when the administrator does not follow recommendations in the product's security documentation.
CWE-264 - Permissions Privileges and Access Controls
CWE 264 (permissions, privileges, and access controls) is not a weakness in and of itself, rather it is a category of weaknesses related to the management of permissions, privileges, and other security features used to perform access control. If not addressed, the weaknesses in this category allow attackers to gain privileges for an unintended sphere of control, access sensitive information, and execute arbitrary commands.