If you use solutions from jailbreak for a long time, then you probably know that the application of such software involves the removal of many security measures implemented by Apple Lossless Audio CODEC (ALAC), in your operating system. To obtain administrator access in iOS, it is necessary to remove these security measures, but one of the unpleasant effects is that iOS becomes vulnerable. We found out how vulnerable iOS can be at the launch evasi0n7, hackers "accidentally" leaving a backdoor in their software, allowing access to iDevices and running various commands.
Unfortunately, things like this can happen in the future, but we don't have to limit ourselves only to problems like this when it comes to security. I told you just a few months ago that the developer of a tweak was making money from users by displaying ads in a hidden window in iOS, all without the users knowing what was happening in the system. In the same way, the applications from Cydia can implement various unexpected changes, Activator displaying, for the first time, advertisements inside the Settings application.
Basically, a Cydia tweak or an application can implement any kind of changes I want in iOS, can transmit data at will and allow hackers to access our systems, if you don't change your SSH password. Moreover, the use of a jailbreak it can allow a much easier spread of malware, if hackers were interested in such a thing, but problems of this kind come together with freedom, the freedom to do whatever we want, whenever we want, without Apple being able to limit us.
In short, jailbreak solutions are not secure, but this is the price we pay for freedom.
