A pretty transparent attempt to scare people on the Labour Right into a) mobilising and b) to cast tight preference chains: I personally wouldn't believe even a published poll of this sort of contest, let alone questionable leaks of supposed private 'polling'.
Still, there's no doubt that Corbyn is doing very well; maybe he really will top the poll. Actually winning would be much harder as he's unlikely to be transfer friendly. I think he would need a very large lead on first preferences and for their to be little transferring between the other candidates, which seems like a stretch.
Well if the fear of Corbyn mobilizes the right, and they vote Kendall first pref, maybe -
maybe - a Corbyn vs Kendall last round is a possibility.