Did you think Meltdown was bad? Unprivileged applications being able to read kernel memory at speeds possibly as high as megabytes per second was not a good thing.
Meet the Windows 7 Meltdown patch from January. It stopped Meltdown but opened up a vulnerability way worse … It allowed any process to read the complete memory contents at gigabytes per second, oh - it was possible to write to arbitrary memory as well. – blog.frizk.net