On trying to perform software updates from the Mac App Store users were getting an error message saying, “The certificate for this server is invalid. You might be connecting to a server that is pretending to be “swscan.apple.com” which could put your confidential information at risk.”
Swscan.apple.com is one of the various servers that Software Update uses to communicate with Apple. The security certificate for the server had expired, causing the problem.
Apple has now fixed the issue and users are no more experiencing the error message. The certificate has been renewed for two more years.