How is hacking happening??

One obvious way is to hack third party libraries. Change the codes.

Other one is to change handling of the code in the interpreter.

Other is run a different code  in a hidden manner. Very similar to the original but slightly modified. The output terminals are switched.

Writing to files may also be hacked.

Hacking to monal narsaria ke dalaal hi kar rahein hain. Saali ne pata nahi kis kis ko apni baati hai. Yeh srk Randi ka group bhi hacking Mei involved lagta hai.

Sunder pichai bhi usi ka dalaal hai.