Apple just released iOS 11.2.2 and macOS High Sierra 10.13.2 with some Safari and WebKit improvements to mitigate the Spectre vulnerability. you should update your devices with the latest security patches.
iOS 11.2.2 includes “Security improvements to Safari and WebKit to mitigate the effects of Spectre,” the company writes on its support page, while the macOS High Sierra 10.13.2 Supplemental Update does the same for your Mac laptop or desktop. Installing this update on your Mac will also update Safari to version 11.0.2.
Meltdown was already addressed in previous updates. iOS 11.2, macOS 10.13.2 and tvOS 11.2 already included mitigations for Meltdown. Apple Watch chips aren’t affected by Meltdown.