apps/calendar/ajax/events.php in ownCloud before 4.5.11 and 5.x before 5.0.6 does not properly check the ownership of a calendar, which all…

apps/calendar/ajax/events.php in ownCloud before 4.5.11 and 5.x before 5.0.6 does not properly check the ownership of a calendar, which allows remote authenticated users to download arbitrary calendars via the calendar_id parameter.