[1.8] I can break everything on client-side, but it's doing nothing at server side

[firerocket8]

Hi, I'm coding own client and I changed something.
I don't know what it was. But now I can break and place every block on server which is on client-side.

Can someone help me and tell where I can search for the line or class where I changed it?

[Draco18s]

1.8 is not supported here. Update.

Also:

4 minutes ago, firerocket8 said:

I'm coding own client

Don't do this.