When going to Settings, Website UI, and then adjusting any of the style settings and clicking on the Save changes button, I get a 403 Forbidden error and no changes are saved.
E.g. I see a list of styles, I click on H1 style, then scroll down, and click on Text Color. I choose a new colour and click OK, then click on the Save Changes button.
Response is "403 Forbidden
Access to this resource on the server is denied!"