Nextcloud: xss for admin of https://newsletter.nextcloud.com

a site https://newsletter.nextcloud.com to have phplist 3.2.5 steps to reproduce: 1. to use firefox browser, latest version 2. go to https://newsletter.nextcloud.com/admin/?page=viewtemplate&id=123%22%3E%3Cscript%3Ealertdocument.domain%3C/script%3E 3. log in as admin 4. alert box with name of...