Several readers have noted a strange error message appearing when trying to perform software updates from the Mac App Store.

An Error has occurred
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 you confidential information at risk.
Swscan.apple.com is one of several servers that Software Update uses to communicate with Apple. The apparent problem is that the security certificate for the server appears to have expired. The certificate was originally valid from May 22, 2012 to May 24, 2014.

This is a problem that Apple will need to fix on their side. In the meanwhile, users can manually download updates from Apple's support site.
Update: This may also be the cause of NSURLErrorDomain error -1012, which appears to have started in the same time.
Update 2: Apple appears to have fixed the certificate.














Top Rated Comments
"Siri, Remind me to renew SSL Certificate for Swscan.apple.com on May 23. Alert me two days before, and alert me a second time on the day before."
And now Tim Cook should just say to Siri:
"Siri, Remind me to fire the guy in charge of swscan.apple.com on Monday, May 26th."
You forgot:
Microsoft Forgets to Renew... = Yet another example of a top-heavy corporation unable to keep even simple things in check. Thank goodness Apple hasn't forgotten its user base.
Apple Forgets to Renew... = Calm down, people; non-issue. Do you even realize how much time a big company needs to address things like this?
Isn't there at least one person, at Apple, whose job is to keep things like that up-to-date?
Did I catch everything?