The platform does not filter input and encode output in Quick Post validation error message, which can deliver an XSS payload.
Old CVE fixed the XSS in label HTML but didn’t fix it when clicking save.
In Quick Post, click save with blank slug; The XSS will be executed
"errors":{"title":["<script>alert('nono')</script> cannot be blank."],"slug":["Slug cannot be blank."]
Fixed in https://github.com/craftcms/cms/commit/9d0cd0bda7c8a830a3373f8c0f06943e519ac888