Advanced Custom Fields: Extended 0.8.9.4 - 0.9.2.7 - Contributor+ XSS via Form Shortcode Attributes

The Advanced Custom Fields: Extended WordPress plugin before 0.9.2.8, Advanced Custom Fields: Extended PRO WordPress plugin before 0.9.2.8 does not validate or escape some of its form shortcode attributes, which can be pointed at values taken from the visitor's own request and are then output without escaping, allowing users with a role as low as contributor to have arbitrary script run in the browser of anyone led to open a crafted link or page, including a logged-in administrator.
This is an incomplete fix for CVE-2023-5292, whose deny-list covers only the three HTML wrapper attributes.