Sure, but the weakness is exploited using physical connection between the device and a computer ( I remember one or two jailbreaks in history were opening a pdf

Sure, but the weakness is exploited using physical connection between the device and a computer ( I remember one or two jailbreaks in history were opening a pdf or something like this, but nowadays those are history as well ). And when you actually exploit this weakness, next phase is installing apps that can exploit your whole phone. Back in time I was keen on jailbreaking my device, because I wanted to see bash prompt and do whatever I want with it, but nowadays I left this for non-used devices that I have. I'm pretty concerned with security after the whole NSA revelations and I believe my device is more secure if it's not jailbreaked.