Earlier today Apple released a new version of macOS High Sierra with additional patches for Specter and Meltdown vulnerabilities.
Now the company has also released updates for macOS Sierra 10.12.6 and El Capitan 10.11.6, which are already available for download on Mac App Store under the Updates tab. To download and install updates, select the one you want and follow the subsequent on-screen instructions.
The new patch Apple has been named Security Update 2018-001.
Below is the postscript to the update:
Available for: macOS Sierra 10.12.6, OS X El Capitan 10.11.6
Description: Microprocessor-based systems that use speculative instruction execution and advanced branch prediction can allow hackers to gain access to information via a third-party channel in the form of a shared cache hierarchy.
In addition to the Specter and Meltdown patches, the security update contains solutions to other issues, including a fix for a bug that allows malware to extract arbitrary code, etc.
Updates for macOS Sierra and El Capitan are now available on Mac App Store.