GHSA-gc5h-6jx9-q2qh: eZ Platform Admin UI vulnerable to DOM-based Cross-site Scripting in file upload widget

The file upload widget is vulnerable to XSS payloads in filenames. Access permission to upload files is required. As such, in most cases only authenticated editors and administrators will have the required permission. It is not persistent, i.e. the payload is only executed during the upload. In effect, an attacker will have to trick an editor/administrator into uploading a strangely named file. The fix ensures XSS is escaped.