How to use localStorage variable in safe?

Question

Iam tray to use isAuthenticated useState in all component to stop users traying to set url of any other component but I think it is not safe to storage localStorage.getItem('user'); in localStorage how to fix or is there any other way to do this ?

const [isAuthenticated, userHasAuthenticated] = useState(localStorage.getItem('user') ||'false');
        
                useEffect(() => {
                    var x =localStorage.getItem('user');
                     if (x=='false'){
                        window.location.assign("/");
                        }else{
                            console.log("ok");
                        }
                  }, []);