Did Not Connect: Potential Security Issue Firefox detected a potential security threat and did not continue to player.vimeo.com because this website requires a secure connection. What can you do about it? player.vimeo.com has a security policy called HTTP Strict Transport Security (HSTS), which means that Firefox can only connect to it securely. You can’t add an exception to visit this site. The issue is most likely with the website, and there is nothing you can do to resolve it. You can notify the website’s administrator about the problem.