A very strange thing happend on December 19th, 2017. The price of Coinbase bitcoin cash (BCH) jumped up almost 4 times while other crypto exchanges were going up also (only 50% to 100%) but not so fast. All the figures of cryptos were negative on coinmarketcap except for one coin, Yes you guess it: Bitcoin Cash
All kind of speculations were in the air about pump and dump (a way to inflate the price artificially and sell for a great price leaving the other people with an asset that is not in line with the real market price).
WTF happened with coinbase?
There was something going on with coinbase where the previous owners of Bitcoin would receive their Bitcoin cash coin if they owned Bitcoin on coinbase before August 1st 2017.
Trading (buying and selling) was halted on coinbase. The strange price was a result of adding Bitcoin cash to the user accounts.
More information about this change can be found on the coinbase FAQ support page.
It will stay a mysterie for now what really happend on the market (all major crypto coins down and a price jump of 100% for Bitcoin cash in a few hours).
Insider market knowledge
Will be added later when this strange event has been investigated further.
Cryptovest about Suspicions of Insider Trading for Bitcoin Cash