diff --git a/handler/routes.go b/handler/routes.go
index a2ceeaf..c0413d4 100644
--- a/handler/routes.go
+++ b/handler/routes.go
@@ -8,6 +8,7 @@ import (
 	"io/fs"
 	"net/http"
 	"os"
+	"regexp"
 	"sort"
 	"strings"
 	"time"
@@ -26,6 +27,8 @@ import (
 	"github.com/ngoduykhanh/wireguard-ui/util"
 )
 
+var usernameRegexp = regexp.MustCompile("^\\w[\\w\\-.]*$")
+
 // Health check handler
 func Health() echo.HandlerFunc {
 	return func(c echo.Context) error {
@@ -63,6 +66,10 @@ func Login(db store.IStore) echo.HandlerFunc {
 		password := data["password"].(string)
 		rememberMe := data["rememberMe"].(bool)
 
+		if !usernameRegexp.MatchString(username) {
+			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid username"})
+		}
+
 		dbuser, err := db.GetUserByName(username)
 		if err != nil {
 			return c.JSON(http.StatusInternalServerError, jsonHTTPResponse{false, "Cannot query user from DB"})
@@ -135,9 +142,12 @@ func GetUsers(db store.IStore) echo.HandlerFunc {
 // GetUser handler returns a JSON object of single user
 func GetUser(db store.IStore) echo.HandlerFunc {
 	return func(c echo.Context) error {
-
 		username := c.Param("username")
 
+		if !usernameRegexp.MatchString(username) {
+			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid username"})
+		}
+
 		if !isAdmin(c) && (username != currentUser(c)) {
 			return c.JSON(http.StatusForbidden, jsonHTTPResponse{false, "Manager cannot access other user data"})
 		}
@@ -200,12 +210,16 @@ func UpdateUser(db store.IStore) echo.HandlerFunc {
 			admin = false
 		}
 
+		if !usernameRegexp.MatchString(previousUsername) {
+			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid username"})
+		}
+
 		user, err := db.GetUserByName(previousUsername)
 		if err != nil {
 			return c.JSON(http.StatusNotFound, jsonHTTPResponse{false, err.Error()})
 		}
 
-		if username == "" {
+		if username == "" || !usernameRegexp.MatchString(username) {
 			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid username"})
 		} else {
 			user.Username = username
@@ -261,7 +275,7 @@ func CreateUser(db store.IStore) echo.HandlerFunc {
 		password := data["password"].(string)
 		admin := data["admin"].(bool)
 
-		if username == "" {
+		if username == "" || !usernameRegexp.MatchString(username) {
 			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid username"})
 		} else {
 			user.Username = username
@@ -303,6 +317,10 @@ func RemoveUser(db store.IStore) echo.HandlerFunc {
 
 		username := data["username"].(string)
 
+		if !usernameRegexp.MatchString(username) {
+			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid username"})
+		}
+
 		if username == currentUser(c) {
 			return c.JSON(http.StatusForbidden, jsonHTTPResponse{false, "User cannot delete itself"})
 		}
@@ -357,6 +375,11 @@ func GetClient(db store.IStore) echo.HandlerFunc {
 	return func(c echo.Context) error {
 
 		clientID := c.Param("id")
+
+		if _, err := xid.FromString(clientID); err != nil {
+			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid client ID"})
+		}
+
 		qrCodeSettings := model.QRCodeSettings{
 			Enabled:       true,
 			IncludeDNS:    true,
@@ -485,6 +508,10 @@ func EmailClient(db store.IStore, mailer emailer.Emailer, emailSubject, emailCon
 		c.Bind(&payload)
 		// TODO validate email
 
+		if _, err := xid.FromString(payload.ID); err != nil {
+			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid client ID"})
+		}
+
 		qrCodeSettings := model.QRCodeSettings{
 			Enabled:       true,
 			IncludeDNS:    true,
@@ -536,6 +563,10 @@ func UpdateClient(db store.IStore) echo.HandlerFunc {
 		var _client model.Client
 		c.Bind(&_client)
 
+		if _, err := xid.FromString(_client.ID); err != nil {
+			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid client ID"})
+		}
+
 		// validate client existence
 		clientData, err := db.GetClientByID(_client.ID, model.QRCodeSettings{Enabled: false})
 		if err != nil {
@@ -642,6 +673,10 @@ func SetClientStatus(db store.IStore) echo.HandlerFunc {
 		clientID := data["id"].(string)
 		status := data["status"].(bool)
 
+		if _, err := xid.FromString(clientID); err != nil {
+			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid client ID"})
+		}
+
 		clientData, err := db.GetClientByID(clientID, model.QRCodeSettings{Enabled: false})
 		if err != nil {
 			return c.JSON(http.StatusNotFound, jsonHTTPResponse{false, err.Error()})
@@ -667,6 +702,10 @@ func DownloadClient(db store.IStore) echo.HandlerFunc {
 			return c.JSON(http.StatusNotFound, jsonHTTPResponse{false, "Missing clientid parameter"})
 		}
 
+		if _, err := xid.FromString(clientID); err != nil {
+			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid client ID"})
+		}
+
 		clientData, err := db.GetClientByID(clientID, model.QRCodeSettings{Enabled: false})
 		if err != nil {
 			log.Errorf("Cannot generate client id %s config file for downloading: %v", clientID, err)
@@ -700,6 +739,10 @@ func RemoveClient(db store.IStore) echo.HandlerFunc {
 		client := new(model.Client)
 		c.Bind(client)
 
+		if _, err := xid.FromString(client.ID); err != nil {
+			return c.JSON(http.StatusBadRequest, jsonHTTPResponse{false, "Please provide a valid client ID"})
+		}
+
 		// delete client from database
 
 		if err := db.DeleteClient(client.ID); err != nil {
diff --git a/model/wake_on_lan_host.go b/model/wake_on_lan_host.go
index 2d1ab73..73966f0 100644
--- a/model/wake_on_lan_host.go
+++ b/model/wake_on_lan_host.go
@@ -2,6 +2,7 @@ package model
 
 import (
 	"errors"
+	"net"
 	"strings"
 	"time"
 )
@@ -18,7 +19,13 @@ func (host WakeOnLanHost) ResolveResourceName() (string, error) {
 		return "", errors.New("mac Address is Empty")
 	}
 	resourceName = strings.ToUpper(resourceName)
-	return strings.ReplaceAll(resourceName, ":", "-"), nil
+	resourceName = strings.ReplaceAll(resourceName, ":", "-")
+
+	if _, err := net.ParseMAC(resourceName); err != nil {
+		return "", errors.New("invalid mac address")
+	}
+
+	return resourceName, nil
 }
 
 const WakeOnLanHostCollectionName = "wake_on_lan_hosts"
diff --git a/store/jsondb/jsondb.go b/store/jsondb/jsondb.go
index 4ccd9b7..b961e95 100644
--- a/store/jsondb/jsondb.go
+++ b/store/jsondb/jsondb.go
@@ -38,12 +38,12 @@ func New(dbPath string) (*JsonDB, error) {
 func (o *JsonDB) Init() error {
 	var clientPath string = path.Join(o.dbPath, "clients")
 	var serverPath string = path.Join(o.dbPath, "server")
+	var userPath string = path.Join(o.dbPath, "users")
 	var wakeOnLanHostsPath string = path.Join(o.dbPath, "wake_on_lan_hosts")
 	var serverInterfacePath string = path.Join(serverPath, "interfaces.json")
 	var serverKeyPairPath string = path.Join(serverPath, "keypair.json")
 	var globalSettingPath string = path.Join(serverPath, "global_settings.json")
 	var hashesPath string = path.Join(serverPath, "hashes.json")
-	var userPath string = path.Join(serverPath, "users.json")
 
 	// create directories if they do not exist
 	if _, err := os.Stat(clientPath); os.IsNotExist(err) {
@@ -52,12 +52,12 @@ func (o *JsonDB) Init() error {
 	if _, err := os.Stat(serverPath); os.IsNotExist(err) {
 		os.MkdirAll(serverPath, os.ModePerm)
 	}
-	if _, err := os.Stat(wakeOnLanHostsPath); os.IsNotExist(err) {
-		os.MkdirAll(wakeOnLanHostsPath, os.ModePerm)
-	}
 	if _, err := os.Stat(userPath); os.IsNotExist(err) {
 		os.MkdirAll(userPath, os.ModePerm)
 	}
+	if _, err := os.Stat(wakeOnLanHostsPath); os.IsNotExist(err) {
+		os.MkdirAll(wakeOnLanHostsPath, os.ModePerm)
+	}
 
 	// server's interface
 	if _, err := os.Stat(serverInterfacePath); os.IsNotExist(err) {
@@ -149,12 +149,6 @@ func (o *JsonDB) Init() error {
 	return nil
 }
 
-// GetUser func to query user info from the database
-func (o *JsonDB) GetUser() (model.User, error) {
-	user := model.User{}
-	return user, o.conn.Read("server", "users", &user)
-}
-
 // GetUsers func to get all users from the database
 func (o *JsonDB) GetUsers() ([]model.User, error) {
 	var users []model.User