If you're not an Apple Developer, you can still download the macOS High Sierra 10.13.5 update from the Mac App Store:
If you need the for compatibility or legacy software, specify that. Otherwise, Apple’s final High Sierra version (10.13.6) is more common and secure. download macos high sierra 10135 image file rdr hot
: You can find the macOS High Sierra installer on the Mac App Store using a direct link in Safari. If you're not an Apple Developer, you can