Ghost is a Node.js content management system. From 6.22.1 until 6.64.0, Ghost restricted the content type used to serve uploaded files to prevent browsers from executing them. On sites using the default local storage adapter, this restriction was not applied, so files uploaded by any staff user were served with a content type derived from their file extension. This could be used to host scripts on the site's domain, possibly resulting in compromise of other staff users' admin sessions. This issue is fixed in version 6.64.0.