Jailbreaking is where you exploit a security hole, or more likely a whole series of security holes, in what is essentially a carefully orchestrated cybersecurity attack on yourself, in order to liberate yourself from Apple’s locked-down attitude to iPhones.
Want to install your own apps? Want to modify locked system settings? Want to run network services like SSH or even a tiny web server? Want the freedom to delve more deeply into a running system than Apple will let you? Want to patch security holes on old and unsupported devices?
In iOS 12.4, released last month, Apple fixed a number of security bugs, as well as enabling support for the Apple Card in the US. But in doing so, the company accidentally reversed a security fix it had previously patched in iOS 12.3 at the end of April.
People using iOS 12.4 or iOS 12.2 and below should be careful with what they download from the App Store in coming weeks because an app could include the jailbreak, according to security researcher Stefan Esser.