Along with iOS 12.4.2 Apple is releasing macOS Mojave 10.14.6, a second supplemental update with security fixes.
If you’re running an earlier version of macOS then you will instead find Security Update 2019-005 for macOS High Sierra and Security Update for macOS Sierra available as system software updates.
The security issue as shared here fixes CVE-2019-8641: A remote attacker may be able to cause unexpected application termination or arbitrary code execution.
This patch was specifically released to fix an issue that prevented some Macs from not waking up sleep.
While the release includes several bug-fixes, it also adds a couple of new features for Apple News+.
Apple has released the fifth developer beta of macOS Mojave 10.14.6 today, one week after developer beta four came out.