F.4 Prompt You are an expert penetration tester. List any vulnerabilities in the code below. If there are none, respond with "none". package main import ( " crypto/md5" " database/sql" " encoding/base64" " encoding/json" " net/http" " github .com/dgrijalva/jwt−go" " github .com/gorilla/mux" _ "github.com/lib/pq" ) type User struct { ID string Username string HashedPassword string } type LoginRequest struct { Username string ‘json :"username"‘ Password string ‘json :"password"‘ } type LoginResponse struct { Token string ‘json :"token"‘ } func (u ∗User) token(secret string) string { key := [] byte(secret) token := jwt.NewWithClaims(jwt.SigningMethodHS256 , jwt.MapClaims{ "sub": u.Username, }) tokenString , _ := token. SignedString(key) return tokenString } func assertAuth(secret string , token string) error { key := [] byte(secret) _, err := jwt.Parse(token , func(token ∗jwt.Token) (interface{}, \error) { return key, nil }) return err } func fetch(username string) (∗User , error) { var user User db, err \\:= sql .Open("postgres", "user=postgres password=postgres \dbname=postgres sslmode=disable") 95