How did this happen?

I've had some tool use my membership sign up form, but what they've done is create an automated email response that doesn't match my database fields. How have they managed to achieve this:

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Form Submitted: 11-22-2014 | 3:39 AM UTC

title: bonnet visiere timberland
url: http://www.capteo.com/wp-content/cache/meta/fr-timberland/OnEhFf7axM/
excerpt: Can you tell us more about this? I'd want to find out some additional information.
blog name: bonnet visiere timberland
Email Verification Link:
http://www.showmetransport.com/user-verified.php?id=&randomString=c7qck8ot7b&email=

The only field in this that matches my database is Email Verification Link

What have they done to override my info, how have they managed to get past my required fields, and what should I be looking for if I've been subjected to some sort of cyber attack?

No entry has been made to the users table in the database, so I am concerned that I need to know what else may be afoot!

Thanks.

most likely you are using different triggers int he Behaviors for sending the email, and Validating / inserting to the database.

Make sure that all the behaviors use the same trigger.

if it is set up where validation uses a trigger Button Submit pressed, and the email behavior is set to any form post, it can pretty easy to get around the validation, an attacker would save the source of your page to a local copy, then edit the name of the submit button and change the form action to post to the page on your site.

By changing the submit button name, they by pass the validation, but still trigger sending the email.

I've not looked to see if that's the problem, but regardless of how they've achieved it, is it possible for them to have done something malicious? What should I look for?

Thanks.

No, I don't believe they have done anything malicious other then send the email

OK, thank you for your advice on this. Hacking isn't my forte, I wouldn't even know where to start doing it, as a result, I don't really know how to defend against it other than ensure I have strong passwords etc.

You're welcome.