Coinbase (COINB) confirms that it filed preliminary documents with the SEC for an IPO.The crypto exchange was valued at ~$8B in its last private funding round in October 2018, according to CNBC.The company, which started in 2012, now has more than 35M users and more than $320B of volume is traded on its platform, according to the Coinbase's website.The move comes as bitcoin's recent surge past $20K and challenged $24K today before pulling back.Bitcoin price picks up steam since mid-October: