Rock Lobster Contact Form 7 before 3.7.2 allows remote attackers to bypass the CAPTCHA protection mechanism and submit arbitrary form data by omitting the _wpcf7_captcha_challenge_captcha-719 parameter.
contactform7.com/2014/02/26/contact-form-7-372/
web.archive.org/web/20140727133642/http://www.hedgehogsecurity.co.uk/2014/02/26/contactform7-vulnerability/
wordpress.org/plugins/contact-form-7/changelog
www.acunetix.com/vulnerabilities/web/wordpress-plugin-contact-form-7-security-bypass-3-7-1/
www.cvedetails.com/cve/CVE-2014-2265/