Hello there folks!
We were just informed that the security certificate for our website and forums is about to expire, likely this week. Unfortunately we need our server admin to do renew it, but they are not able to do that this week. While we wait for that, an error message like this can occur on our sites and forums.
This does not mean that our site is compromised, but that the certificate that browsers use to establish a secure connection is not available.
Here's a Microsoft support page regarding the error message.