C/C++ was indeed considered high level but some years ago, right now it's considered low-level due to the possibility of editing memory directly.
High level would be Java with a good syntax, lots of stack, buffer protections and other stuff, like VB.
Anyways for those starting I hope you find what you're looking for.
As for WebApp I must say, it will get kinda straight after some reading, as you'll find out most of vulnerabilities are just due to user input and a poor validation, which means that from there you'll only need to know how to code in the vulnerable language to exploit it.
iHackiDevices I wish you luck, you just know your way around C/C++, Assembly, look into reverse engineering and should also check Overfows, heap, stack, buffer.
After all that you just have to defeat the protections such as ALSR, DEP which protect systems from overflowing.
I must say, you're going into the hardest, but also the biggest reward, so good luck