Shares of software maker Rocket Fuel (FUEL), which provides tools to ad buyers, today closed up 44 cents, or 21%, at $2.55, after CNBC yesterday reported that U.S. Republican presumptive presidential nominee Donald Trump has been using the company’s software to track online user behavior and target his pitch, citing software the news channel probed for clues.

As CNBC’s Ari Levyrelates, in a print piece, "CNBC.com learned of the addition by using Ghostery, a browser plug-in that shows all the data tracking tools running on...