Turn 10 Studios and Microsoft have a strict anti-cheat system. Using a modified "online" version will likely lead to a permanent ban of your Xbox/Microsoft account .
Versions labeled with specific build numbers (like v1.517.253.0) on third-party sites often contain: Dowload Forza Horizon 5 v1.517.253.0 OnLine
If you are looking for a deal, check the Microsoft Store or Steam during seasonal sales, where the game is often discounted by 50% or more. Turn 10 Studios and Microsoft have a strict