Stored XSS in CardDAV image export (NC-SA-2016-008)

The CardDAV image export functionality as implemented in Nextcloud allows the download of images stored within a vCard. Due to not performing any kind of verification on the image content this is prone to a stored Cross-Site Scripting attack.Note: Nextcloud employs a very strict Content Security Policy on the DAV endpoints. This is thus only exploitable on browsers that don’t support Content Security Policy.