I've seen a bug yesterday on coinmarketcap but it just happened within few minutes. Bitcoin was gone on the list and ethereum became the number 1 while XRP became number 2.
XRP is ranked as 3rd but it's highly unlikely to see it as number 1.
XRP is still among the top 5 altcoins in the coinmarketcap but I remember a few months back when the total circulation exceeded the marketcap of teh Etherum. I have seen the same complaints posted by the Reddit members and the bug is related to the fake volume coming from disparate sources. API trading volumes are not representing the truth and the coinmarketcap have no choice except accepting this data. That's why some warnings appear while looking at the page of exchanges and this warning are reported by the website users.
I've seen that report about the manipulation from CMC and what's more interesting is that XRP became 2nd before without any manipulation.
But I think right now they became more aware of those reports that were sent to them.