About Apple security updates
For our customers' protection, Apple doesn't disclose, discuss, or confirm security issues until an investigation has occurred and patches or releases are available. Recent releases are listed on the Apple security updates page.
For more information about security, see the Apple Product Security page. You can encrypt communications with Apple using the Apple Product Security PGP Key.
Apple security documents reference vulnerabilities by CVE-ID when possible.
Xcode 9.3
Released March 29, 2018
LLVM
Available for: macOS High Sierra 10.13.2 or later
Impact: Multiple issues in llvm were addressed in this update
Description: Multiple issues were addressed by updating to version the current version of LLVM shipping with Xcode.
CVE-2018-4164: found by OSS-Fuzz