Shares of Opendoor Technologies ( OPEN -10.44%) have caught fire in the last month. Driven by investors posting online about buying the penny stock, it is now up 325%, with most of the gains coming in the past week.

A Meteoric Surge Ignites Hype Opendoor Technologies (NASDAQ:OPEN) is on fire, skyrocketing 75% in midday trading Monday, after a jaw-dropping 188% gain last week, lifting its stock to $3.94 per share.

Opendoor stock took off last Monday after Eric Jackson, founder of EMJ Capital, announced his firm had taken a position in the company and said the stock “could be a 100-bagger over the next few years.” The term refers to stocks that return $100 for every $1 invested.