I have a newsletter subscription form on a website using Kentico 9. There is a simple captcha : "prompts users to retype a sequence of numbers from an image". Since a few month, I have noticed a lot of new subscriptions with email address that can look real because of the domain. But names attached to the email address are only a series of letters (example : vPkGNFtUjyxcEQ). I verified some email address on CleanTalk and they were reported as spam.Is it possible for bots to subscribe to the newsletter even with this kind of captcha? How can I prevent that? Thanks!
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