fault in builtin sort()?

I would like to give some feedback about ...

From: https://js.checkio.org/mission/median/solve/

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Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:50.0) Gecko/20100101 Firefox/50.0

I have already asked a question on the forum. However, I am reasonably certain it's a bug, I tried various ways e.g. data.sort(function(a,b){return a>b}); data.sort(function(a,b){return (a-b)<0}); and every time the array [10,9,8,7,6,5,4,3,2,1,0] was sorted as [5,0,1,2,3,4,6,7,8,9,10]

over to ya...