Please see comments.
Some of my Joomla! sites use Facile Forms to manage their forms. This extension is getting a little aged and the developer has indicated he might not upgrade the code for new versions of Joomla!.
Recently, a Facile Forms user complained they were receiving form spam. (Form spam is similar to email spam only the spammer uses website forms to insure delivery to real users.) Facile Forms has a security code CAPTCHA to block form spam but obviously it was not working. So I removed the Facile Form CAPTCHA and implemented a different CAPTCHA.