After the security vulnerabilities Meltdown and Spectre were unveiled early last month, it became clear that we're going to be updating our devices for a long time. Requiring both firmware and software patches to mitigate, there was going to be a performance impact, which Intel promised would reduce in the long run.
Today, Intel announced that it's releasing another update, which is for sixth- (Skylake), seventh- (Kaby Lake), and eighth-generation (Coffee Lake) processors. This includes the Core X-series, Xeon Scalable and Xeon D chips as well.
The new microcode will be made available through OEM firmware updates. That means that instead of getting them through Windows Update, you'll want to use the third-party utility that came with your PC to get the new firmware. For example, on Lenovo PCs, there's an app called Vantage, and HP devices have Support Assistant.
OEMs are getting the new code today, so you won't see the new firmware on your PC just yet. As is always recommended though, you should regularly check for new updates on your device.