https://www.bleepingcomputer.com/news/security/apple-releases-ios-1241-to-patch-security-flaw-behind-jailbreak/

Apple released iOS 12.4.1 today to fix a security flaw reintroduced with the release of iOS 12.4, and used by security researcher Pwn20wnd to develop and release a jailbreak tool for up-to-date iOS devices.

The vulnerability patched today by Apple is a use after free tracked as CVE-2019-8605 targeted by the Sock Puppet exploit that was used to create jailbreak tools for iOS devices.