How to Resolve Security Warnings on Form Submissions
If you receive a security warning like the one above when you submit a form over your SSL-enabled site, do not be alarmed.
Nothing is wrong with your SSL certificate.
Your site is most likely submitting the form from an HTTPS page to an HTTP page. When this happens, browsers will flag it with a security warning.
To fix this problem, find the action URL of the form and fix it to submit to an HTTPS page rather than an HTTP page.