For bugs, codechef has provided a separate mailing address "bugs@codechef.com" where you can contact them. I had also informed them about wrong voting count about two month ago but they haven’t fixed it yet.
Don’t know anything about 1st Bug But 2nd one is working fine. You come across this because of caches not cleared in your browser. Try Ctrl + Shift + R (to clear caches and refresh) you will see no such issues.
Codechef team doesn’t seem to be very responsive to emails , I have also reported 1 or 2 bugs but haven’t got any response from them , they got to improve this.
I have reported the first bug to Codechef and they told that they are aware of the bug but haven’t fixed it yet and the login system is working fine for me.