Multiple cross-site scripting (XSS) vulnerabilities in ownCloud 4.5.5, 4.0.10, and earlier allow remote attackers to inject arbitrary web script or HTML via the (1) unspecified parameters to apps/calendar/ajax/event/new.php or (2) url parameter to apps/bookmarks/ajax/addBookmark.php.
https://owncloud.org/security/advisories/multiple-xss-vulnerabilities-3/