loadstring() Is not available?

So I made a script builder script, because i'm a fan of script builder, And it gives me this error: "loadstring() is not available"

The script is this:

function Clicked()

    if script.Parent.Parent.Execute.Text ~= nil then
        spawn(function()
            loadstring(script.Parent.Parent.Execute.Text)()
        end)
    end
end


script.Parent.MouseButton1Click:connect(Clicked)

And the error is at the line 5: "loadstring(script.Parent.Parent.Execute.Text)()"