CoStar Group, Inc. (CSGP) reported impressive first-quarter revenue of $897 million, a 22.5% increase year-over-year, and doubled its adjusted EBITDA to $132 million. However, the stock faced a 5% decline as market analysts assigned it a Zacks Rank of #4 (Sell), citing missed EPS estimates despite surpassing revenue forecasts. The company remains optimistic, reaffirming its full-year revenue guidance of $3.78 to $3.82 billion.