Today, Apple released updates that will protect some older operating systems (Sierra and El Capitan) against the Meltdown vulnerability.
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.
Patches for High Sierra were released earlier this month. Now Sierra and El Capitan will be protected as well.
This update also fixes other serious security vulnerabilities, including an issue that could cause an application to run arbitrary code using kernel privileges by exploiting a vulnerability on the IOHIDFamily API. It also patches an issue that could lead to arbitrary code execution when playing a malicious sound file.