This update does not list any particular security fixes in the patch log. But it is meant to eliminate and patch a kernel vulnerability that was used by the recent Unc0ver jailbreak.
UncOver is a jailbreak that will unlock any iOS device running iOS 11.0 - 13.5. So if you install the latest update to your device, no more jailbreak for you.
Jailbroken devices can install apps without ads, or TV apps like Kodi which lets you play outside Apple's walled garden. But do it with care. Because sometime if done incorrectly, it can also brick your device.
Click here to install apps from the dark side on your Apple Devices without a jailbreak!