I've been watching the logs of some sites, as I deal with these pesky spambots trying to get around the reCaptcha3 thing on Umbraco Forms, when I encountered a warning I'd not seen before:

WARN: Umbraco.Web.UmbracoHelper : "A value was detected in the ufprt parameter but Umbraco could not decrypt the string"

I have no idea what this is referring to, as there is no other info logged around the same time.

I checked the indicated source - and can see the cause of the exception, but not the reason for it being thrown - i.e. what's going on there and what is being checked.

Anyone?