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.
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Apple security documents reference vulnerabilities by CVE-ID when possible.
Released December 13, 2017
Available for: iPhone 5s and later, iPad Air and later, and iPod touch 6th generation
Impact: A remote attacker may be able to unexpectedly alter application state
Description: A message handling issue was addressed with improved input validation.
CVE-2017-13903: Tian Zhang