I earlier commented on the announcement post of Codeforces Round #655(Div 2) that there many telegram groups in which people are sharing hints to problems and source code during ongoing contests. You can find a lot of posts about this on Codechef Discussion Forum as this happens everytime during Codechef Long Challenge.

But, these people didn't stopped here, the same thing happened during Facebook Hackercup Qualification Round.

Group Link -> Codechef Codeforces Discussion

I am sharing the proofs in the images below:

Therefore, you will find lot of people have correct submission C and D1 in 1-2 hours before the end of the contest.

I request everyone to report such groups otherwise same thing is going to happen in Round 1 too.