CoStar Group is being removed from the Nasdaq-100 Index, with Lumentum Holdings stepping in, as the company grapples with a 53.9% stock value decline over the past year. Despite recent financial improvements, including a small profit of $3 million and a reaffirmation of revenue guidance, CoStar faces ongoing competitive challenges in residential markets. The firm remains undervalued by 42% against intrinsic value estimates, suggesting possible investor opportunities even as it struggles for stability.