flexible-captcha

You can input whatever you want and captcha will accept it. The plugin also cannot be deleted. I hope it was not a malware.

A simple, useful, cool Captcha plugin.

The developer for this plugin was very helpful in getting the plugin to work with a custom form builder plugin and the plugin itself has great options to change the captcha to better suit your needs and has helped cut back on spam. A great plugin to use and really earns the name Flexible Captcha.

best Captcha plugin

If you like this plugin then this isn't an issue, but if you find no use for this plugin after installing. This plugin can't not be delete from the admin panel (Error in uninstalling) or phpmyadmin. I was told the only way to possible delete this plugin is by ftp/sftp. Which I can't/don't have access to. So stay away from this plugin.