A research firm shorts Roblox because the game company is allegedly misleading investors, lying about user numbers, and facilitating illicit behavior with minors. Roblox denies the accusations.

On Tuesday, Roblox—the gaming platform popular with Gen Z and Gen Alpha—saw its stock take a dive. Roblox stock fell 9.4% in early trading, even as it’s already dropped by 15% this year. As of midday ...