The title is misleading at best. The quote per the article is : "Although there are no known exploits affecting customers at the time of this writing, customer

The title is misleading at best. The quote per the article is : "Although there are no known exploits affecting customers at the time of this writing, customers with computers at heightened risk or who run untrusted software on their Mac can optionally enable full mitigation to prevent harmful apps from exploiting these vulnerabilities. Full mitigation requires using the Terminal app to enable an additional CPU instruction and disable hyper-threading processing technology." Not all Macs are affected by this patch and the reduce in performance will affect those with a hyper-threading CPU.