Steps to reproduce:
1) Sign in with an Contributor Account
2) Create a Form and add <img src=x onerror=alert(1) /> to the Help Text or Field Label option of any field
3) The XSS will fire because of the live render. Discard this alert Box and post your Form for review
4) Sign in with your admin account and check the new form in the backend (like when reviewing it).
5) Observe the XSS