If you see KB2919355 being reoffered in your list of Windows Updates today, don't be alarmed. Just about everyone is seeing that.
Since Update 1 for Windows 8.1 and Windows Server 2012 R2 released, there have been multiple fixes made available, but instead of offering them separately, Microsoft has updated KB2919355 to include them. However, when you see KB2919355 offered again, it is smart enough to only install those pieces that you need. It will not reinstall the full update. For me, the reoffer took less than 2 minutes to apply. A reboot is needed, though.
What does this mean for the MSDN and Volume Licensing site downloads? The ISOs have already been replaced to include most of the same fixes. It was replaced on April 15. So, if you downloaded prior to that to build your reference images, you'll need to download it again and replace what you already have stored on-premise. KB2934018 and KB2959977 are still needed to complete the set.
Additionally, the KB Article for KB2919355 has been updated to include explanations for the reoffering.
As I noted yesterday, due to the issues surrounding the KB2919355 released, and a change in servicing policy, Microsoft has extended the deadline for installing the update. Originally just 30 days, the deadline has been pushed to 120 days, with the new target as August 12, 2014. KB2919355 is still a required update and without it, Windows 8.1 and Windows Server 2012 R2 will stop receiving security updates after the deadline. At least, now, companies have a bit more time to become compliant.
For those companies managing update distribution centrally, Microsoft also released a fix to the WSUS bug yesterday that caused the company to halt distribution of the update over HTTPS.