Did you read the entire "Learn More" link?
https://support.mozilla.org/t5/Protect-your-privacy/Insecure-password-warning-in-Firefox/ta-p/27861

It basically says that the website is not using HTTPS for secure logins. Read the whole page at that link.

Its not just Firefox, Google Chrome also presents a "Learn More" link when performing the same login task.
https://support.google.com/chrome/a...093&p=ui_security_indicator&rd=1

And have a quick read through this page from September 2016:
http://money.cnn.com/2016/09/08/technology/google-chrome-flag-non-secure-sites/


How can you fix it?
Purchase an SSL/TLS Cert and upgrade your website from HTTP to HTTPS.

Further reading at:
https://www.verisign.com/en_US/website-presence/website-optimization/ssl-certificates/index.xhtml
and:
https://en.wikipedia.org/wiki/Public_key_certificate
and:
http://info.ssl.com/article.aspx?id=10241


I've purchased SSL Certs several times over the years from these guys:
https://www.SSLs.com/


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