Today, Apple released updates that will protect some older operating systems against the Meltdown vulnerability. Patches for High Sierra were released earlier this month and now Sierra and El Capitan will be protected as well.
The Meltdown and Spectre bugs have been a massive and ongoing issue for the industry. Intel has pledged to patch all recently made chips by the end of the month and faces a number of lawsuits over the vulnerabilities and its handling of them. Congressional leaders have also requested briefings from Intel, AMD and ARM.
You can see the details of Apple's updates here.