If you still insist on investigating these scripts (for educational purposes), learn to identify fakes:
Scripts that claim to "unlock everything" for free are often account-stealers (loggers) hidden in obfuscated code [3]. Risks of Using "Free" Scripts Account Bans: new free gamepass script roblox scripts work
To understand the mechanics of a "Gamepass script," one must distinguish between client-side and server-side processing. If you still insist on investigating these scripts
Place the script inside the ServerScriptService so that the server handles the user's pass privileges. Roblox Creator Hub new free gamepass script roblox scripts work