According to the memo, it seems that Apple has discovered that the late 2013 Mac Pros could have some issue with their graphics cards that could cause distorted video, no video, system instability, freezing, random restarts, shut downs, or booting up problems. The affected Mac Pros are said to have been manufactured between the 8th of February, 2015 to 11th of April, 2015.
Now if you have not experienced any of these issues yourself, you can count yourself lucky. However if you, then we guess you know the culprit of the problem. MacRumors notes that Apple is unlikely to publicly announce this, but will instead get in touch with customers directly, or at least some of them.
So far there seems to be several reports of this problem, like on Apple Support Communities, so it is obvious that there is a problem here. Like we said, if you are affected by this, then you might want to get in touch with Apple who should be able to fix the problem for you for free.