WOW! Apple is leading the game here in software updates. Apple has released iOS 12.4.3 to the devices with did not receive iOS 13. The iPhone 5s and the iPhone 6, which were released in 2013 and 2014 respectively received this update. This update brings in security enhancements and bug fixes to these older devices. This update is highly recommended for all users who have these older iPhone models. This update may also be an attempt to fix the checkm8 jailbreak exploit but Apple cannot actually do it as it is a hardware issue. However, we never know what Apple can do with their software updates. Who knows? They might end up fixing it. The build number for this latest update is 16G130

For now, Just go to Settings>General>Software Update and update to the latest version unless you intend to jailbreak your device in the future.