Silverstripe CMS XSS Vulnerability

SilverStripe CMS before 3.6.1 has XSS via an SVG document that is mishandled by 1 the Insert Media option in the content editor or 2 an admin/assets/add pathname, as demonstrated by the admin/pages/edit/EditorToolbar/MediaForm/field/AssetUploadField/upload URI, aka issue SS-2017-017...