A new form of cheating I speculate might be happening in rounds with points for hacking like today's CF Round 770... The procedure is as follows:
Create an alt account.
Write the correct solution for a problem, say problem A.
Assign an incorrect answer for a particular test case which you speculate might not be in the pretests and write the correct general solution and submit and get AC.
Go to your original account and hack it using that particular test case and get 100 points.
lol when you have points in hack a solution, in that case you cant hack anyone's solution... you will be in a room with 25-30 contestants and you can hack only their solution not anyone's solution...
To hack someone, you should be in the same room with him, and there were 1000+ rooms in today's contest, so the probability of your 2 accounts being in the same room is very less.