Thread:Extension talk:ConfirmEdit/PHP Fatal error: Class 'HTMLFormField' not found in /var/www/vhosts/.../httpdocs/extensions/ConfirmEdit/HTMLCaptchaField.php on line 22/reply (3)

It definitely doesn't support MW 1.11 - I'm not even sure if it supports MW 1.17, or if it's only MW 1.18. That "1.11" should probably be changed - I guess it's there to indicate that there are older versions of ConfirmEdit going back to 1.11; or maybe it's just that no one bothered to change it.