The patch from Apple only offered partial mitigation, though given that there are no known attacks that rely on this exploit, this should not be a cause of concern. However, if you believe your system is at a heightened risk of attack, Apple has posted detailed instructions on how you can enable full mitigation for the MDS vulnerabilities on your Mac.
The partial mitigation from Apple involved updating Safari and other parts of the OS to prevent any such attacks. This is good enough for most users and does not bring about any noticeable decline in performance.
Since there are no known exploits taking advantage of the vulnerabilities, you should really re-consider your decision before enabling full mitigation. That’s because Apple found in its testing that enabling full mitigation can bring about a 40 percent reduction in multi-threaded performance and benchmarks. This should not be surprising since the full mitigation involves disabling hyper-threading which has a negative impact on multi-threaded performance.
The steps to enable full mitigation involve running a few commands in Terminal. The method will work on all Intel-powered Macs running macOS Mojave, High Sierra, and Sierra.
With no known exploit relying on MDS, there really should not be a reason for anyone to go ahead and enable the full mitigation on their Macs. For some reason though, if you are still interested, simply head to the support page linked below and follow the steps. You can always revert the mitigation and enable hyper-threading to restore your Mac to its full performance.
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