When sharing your paper, readers encounter a warning message in their browser.
This message is not being caused by a bug. Most commonly, users who host their papers on custom domains have inadvertently shared their paper using SSL secure protocol (https).
Example: If I share my paper on a custom domain with https://namehere.com, your readers may receive this warning in their browser.
To avoid this warning, we advise users that when sharing their paper to use http protocol, not https.
Https is the secure version of http, the protocol over which very sensitive data is sent between your browser and the website that you are connected to. Https is used to protect and encript highly confidential online transactions like online banking and online shopping forms.
When you request a https connection to a webpage, the website will initially send its SSL certificate to your browser. This certificate contains the public key needed to begin the secure session.
Our SSL certificate works only on *.paper.li subdomains. A custom paper domain does not have a matching SSL certificate so the browser displays the warning message.
For users who would like to use https protocol, we now support SSL encryption but the solution requires that the domain be configured through https://www.cloudflare.com/ssl
It's described here in this forum question.