An authenticated user can upload arbitrary files in the upload function for collection preview images. An attacker may upload an HTML file that includes malicious JavaScript code which will be executed if a user visits the direct URL of the collection preview image (Stored Cross Site Scripting). It is also possible to upload SVG files that include nested XML entities. Those are parsed when a user visits the direct URL of the collection preview image, which may be utilized for a Denial of Service attack. This issue affects edu-sharing: <8.0.8-RC2, <8.1.4-RC0, <9.0.0-RC19.