Cyber.mil serving file downloads using TLS certificate which expired 3 days ago

https://www.cyber.mil/stigs/downloads

Welcome to LWC Communities!

Is there anything inherently insecure about an expired cert other than your browser just complaining about it?
Not inherently, but it can introduce risk. Such as a bad actor using an old expired certificate it was able to acquire to play man-in-the-middle. But if that is happening you have bigger problems.