ownCloud contains a flaw that allows a persistent cross-site scripting (XSS) attack. This flaw exists because the application does not validate the 'site_name' and 'site_url' parameters upon submission to the /apps/external/ajax/setsites.php script. This may allow an attacker 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.