For those who let their computers update themselves automatically, there is a good chance you might have already installed the buggy patch, although thankfully Microsoft has since released a tool in which the patch can be removed. If you'd rather do it manually, you can go to your Control Panel > Programs > Programs and Features > View Installed Updates, and right-click on the KB3004394 update to uninstall it.
If you do not see the patch in the list, then chances are you haven't installed it yet. It is unclear as to how big of a problem this could be for users, but if you have an AMD GPU, AMD's Robert Hallock claims that it could potentially prevent the installation of GPU drivers, so if you'd rather not run into any issues later, you should probably go ahead and remove the update now.
Microsoft has now issued a patch that will remove the faulty update from Windows 7 machines. Users can also remove the update manually by going to Control Panel > Programs > Programs and Features > View Installed Updates, right-clicking on KB3004394 and selecting Uninstall. This will require a restart.
Why this matters: As is often the case with faulty updates, KB3004394 may only affect a subset of users in certain situations. But given that it may prevent future patches from installing, it's worth taking a minute now to wipe it from your machine, even if you haven't noticed any problems yet.