WFFM custom action to update contact details when submit ( for loged in and non loged in users )
This librray will help you to identify and merge contact when a WFFM form submitted.
So, If you ever looked into Sitecore Expierence Profile and notice "Anonymous" records and you asked yourself why this is hapenning then this module will help you to overcome this.
I recomend you to read the following posts to understand the overall problem and solution: