It appears when you try and exit the Roblox game Pet Simulator 99 it attempts to entice you by giving you a free gift. Only applies to new users seemingly. 

Roblox developers are on a another level sometimes 🗿 https://nostrcheck.me/media/fffd169ffb169a88e51065fccee03f8e6c2c02eb15c4bfbe1c477e9db86b43bf/7459943de0112b435cbadb011e2d7187bd2c6b40dd2daa6d96a8126e5cbc2827.webp