Fundstrat Global Advisors head of research Thomas J. Lee, who previously called for bitcoin to hit $6,000 by the middle of 2018 and $25,000 by 2022, has turned cautious after the recent rally "on contemporaneous fundamentals."

Lee says the roughly 60 percent surge in the past month to more than $7,000 is a result of multiple factors, including the CME Group Inc.'s plan to offer futures and speculation Amazon.com Inc. is acquiring crypto-related domain names.

He recommends buying bitcoin in the $5,500 range and the Bitcoin Investment Trust (GBTC) at $750, and is "long-term constructive" on bitcoin, maintaining his 2022 price target of $25,000.

• NOTE: Earlier, Coinbase added more than 100k users in the past 24 hours in the wake of CME’s announcement
• NOTE: Oct. 25, Tom Lee said sees potential for Bitcoin Investment Trust to triple