WebCalendar -- "noSet" variable overwrite vulnerability

Secunia reports:

A vulnerability has been discovered in WebCalendar, which can be exploited by malicious people to compromise a vulnerable system.

Input passed to unspecified parameters is not properly verified before being used with the "noSet" parameter set. This can be exploited to overwrite certain variables, and allows e.g. the inclusion of arbitrary PHP files from internal or external resources.

[source]