The Advanced Custom Fields (ACF®) WordPress plugin before 6.8.11 does not properly sanitize a stored field definition that can be modified through its comment handling, allowing unauthenticated users to inject a payload that is emitted as an HTML attribute name and executed as JavaScript in the browser of any visitor or administrator who views a page rendering the affected field.
https://wpscan.com/vulnerability/f7373dad-036e-47f4-b8a5-584341f66560/