Wouldnt this also expose a device to malicious coders?
If a device has this implemented then is it possible that a simple theme could contain something nasty.
Not trying to stop progress of this project just throwing this out there for consideration.
This is an absolutely valid thought.
In a way: Yes, it is easier to do something malicious with this. With great power comes great risk. The thing is: How would you prevent that? I couldn't think of any way once a module has been loaded, because a) how do you identify something malicious and b) how can you block it when it could just circumvent the security measure taken?
So what I did was to require that you enable a newly installed module in the installer. This at least avoids that you install any normal app and it contains a hidden Xposed module.
And not trying to play this question down, but you could insert malicous code in a theme also when you post a new framework.jar or SystemUI.apk. You could just change the smali code, compile it and you have similar power. For example, modifiying the constructor of the Activity class would also get you into any app and you could as well do whatever you want. You wouldn't even find these modifications because of the hundreds of classes in the Android framework. In this point, Xposed modules are easier to check, because they will usually contain just one class with very few and short methods.
Or take Superuser. Yes, it is asking you every time whether you want to execute this command. But the command can as well be a script that could replace files as the root user. Same for the kernel. In any case, when you modify anything in your phone, there is a risk that it is malicous.
As I said, I'm not denying that there could be a misuse of this project. But I do not see a chance to prevent it without blocking even simple real-life modifications. If anybody has ideas, please let me know.