There are several fundamental bugs that affect almost all CPUs. The issue is that modern computer codes speculate on the outcome of a decision, computing the result both ways (prediction). When the correct decision is determined, the incorrect branch is deleted. The bug allows other processes on the computer to see the content of the deleted branch.
For the home user, these bugs are inconsequential unless your computer has been hacked, and patching them definitely reduces performance 10–30%. But at home, it does not matter which program could access the deleted branch data, because you are in control of all programs (hopefully!).
But on shared computing platforms (the Google, Amazon, and Microsoft clouds), different users are running in separate virtual machines, so your private data could be hacked by another user. This also happens on true multi-user operating systems such as Linux.
So, it would be really good if Apple and Microsoft allowed users to switch off the patch and allow branch speculation to improve performance art minimal risk.
But it is also deeply disturbing that Intel and AMD have not yet fixed the microcode within their CPUs, and have not announced any firm plans to do so in the immediate future. Instead, Intel is deploying a second (the first caused reboots) patch that optionally turns off branch speculation.
Intel just announced that fixed chips will be available later in 2018.
This makes one give pause at the idea of buying a new computer until fixed CPUs are deployed.