Stored XSS triggered by json key during UI generation

How it was found

Stored XSS is triggred from Indices -> Generate a UI Demo. Typing anything in the Primary, Secondary, Tertiary, Image or URL attributes for User Interface section. These text box have a drop down which displays the json keys during which XSS is triggered.

Sample json for XSS would be { "<img src=1 onerror=alert(document.domain)>": "hello", }

Attached: screen shot