includes/functions.php in Craig Knudsen WebCalendar before 1.0.5 does not protect the noSet variable from external modification, which allows remote attackers to set arbitrary global variables via a URL with modified values in the noSet parameter, which leads to resultant vulnerabilities that probably include remote file inclusion and other issues.
PHP remote file inclusion vulnerability in WebCalendar before 1.0.1 allows remote attackers to execute arbitrary PHP code when opening settings.php, possibly via send_reminders.php or other scripts.