Shopify adds in a CAPTCHA to prevent spam signups to the various forms on your website, including the email newsletter signup form, the contact form and "back in stock" notification forms.
This is done through a new page asking the user to "complete the challenge below to help us prevent spam."
These pages are typically only shown if the same user attempts to submit a form more than once in a 24 hour period, though it may be triggered in other cases as well.
For most store owners, this should not be an issue and, in fact, will likely cut down on the amount of spam or fake form submissions you receive.
Keep in mind that, if you're testing your forms, after your first test submission, you will most likely see the warning. However, because most visitors won't be repeatedly submitting forms, this should not be an issue in real world use cases.
Also, once the user clicks the "I am not a robot" button or answers the question displayed in the box, the form will be submitted as normal. This CAPTCHA and is designed to prevent automated programs and spammers from submitting forms.
At this time there is no way to modify this page's design. There is also no setting in Shopify to turn this confirmation page off, but it can be eliminated via one or more of these options:
- Use the embed code provided by your email marketing provider instead of the default form.
- Using a third party form app.
- Use a third party "back in stock" notification app.