I came across this post regarding digital certificates. After Microsoft's trusted Comodo Certificate Authority issued fraudulent certificates that effected many top sites.
So here are some instructions that you can use to protect yourself if you're on a Mac and use Safari as your main browser. Honestly, I don't know how serious this is but if it's got Microsoft's attention, I'd worried somewhat, enough to continue looking into it.
It's amazing this does not happen more often if you ask me. So the instructions provided at Sophos basically enables certificate revocation.
There really isn't much we can do about this. We rely on a system that is based on an honor system and require these security and certificate companies to audit and continually beef up their protocols.
Note: Firefox and IE 9 users should be fine even though Microsoft has issued an update. IE 8 users needs to act to protect themselves.