macOS High Sierra 10.13.2 can be downloaded directly from the Mac App Store or through the Software Update function in the Mac App Store on all compatible Macs that are already running macOS High Sierra.
No major outward-facing changes were discovered in macOS High Sierra 10.13.3 during the beta testing period, but according to Apple's release notes, it brings security and feature improvements.
The update offers additional fixes for the Spectre and Meltdown vulnerabilities that were discovered and publicized in early January and initially fixed in macOS High Sierra 10.13.2.
We also know that the update fixes a bug that allowed the App Store menu in System Preferences to be unlocked with any password. Aside from those changes, Apple's release notes say that the update "addresses an issue that could cause Messages conversations to be temporarily listed out of order."
For more information on the macOS High Sierra operating system, make sure to check out our dedicated macOS High Sierra roundup.
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