Can I add hidden fields to the sign-up forms (I'm probably going to use MailChimp, but this could change) so that I can track where users signed up? I am entirely comfortable doing this in PHP but if I have to hack the plug-in itself, this would cause future update issues.
Ideally I'd like to know what page and/or category they were on. I can then use this on MailChimp to put them on an appropriate list and also to see where sign-ups are coming from.
A filter hook, or, better, a shortcode, perhaps something like [wpsubscribeproform hidden='<?=$category?>' ]
Cheers,
Geoff
