ownCloud contains a flaw that allows a remote cross-site scripting (XSS) attack. This flaw exists because the application does not validate the 'title', 'location', 'description' parameters upon submission to the apps/calendar/lib/object.php script. This may allow a user to create a specially crafted request that would execute arbitrary script code in a user's browser within the trust relationship between their browser and the server.
Remote / Network Access
Loss of Integrity
Upgrade to version 4.0.2 or higher, as it has been reported to fix this vulnerability. An upgrade is required as there are no known workarounds.