diff --git a/web/controller/index.go b/web/controller/index.go
index 82373527..bc371f14 100644
--- a/web/controller/index.go
+++ b/web/controller/index.go
@@ -1,6 +1,7 @@
 package controller
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 	"strings"
@@ -8,6 +9,7 @@ import (
 	"time"
 
 	"github.com/mhsanaei/3x-ui/v2/logger"
+	"github.com/mhsanaei/3x-ui/v2/web/middleware"
 	"github.com/mhsanaei/3x-ui/v2/web/service"
 	"github.com/mhsanaei/3x-ui/v2/web/session"
 
@@ -52,7 +54,7 @@ func (a *IndexController) initRouter(g *gin.RouterGroup) {
 	g.GET("/logout", a.logout)
 
 	g.POST("/login", a.login)
-	g.POST("/register", a.register)
+	g.POST("/register", middleware.RateLimitMiddleware(5, time.Minute), a.register)
 	g.POST("/getTwoFactorEnable", a.getTwoFactorEnable)
 	g.POST("/getTurnstileSiteKey", a.getTurnstileSiteKey)
 }
@@ -130,6 +132,11 @@ func (a *IndexController) register(c *gin.Context) {
 		pureJsonMsg(c, http.StatusOK, false, I18nWeb(c, "pages.login.toasts.invalidFormData"))
 		return
 	}
+
+	// Trim whitespace
+	form.Username = strings.TrimSpace(form.Username)
+	form.Password = strings.TrimSpace(form.Password)
+
 	if form.Username == "" {
 		pureJsonMsg(c, http.StatusOK, false, I18nWeb(c, "pages.login.toasts.emptyUsername"))
 		return
@@ -138,6 +145,14 @@ func (a *IndexController) register(c *gin.Context) {
 		pureJsonMsg(c, http.StatusOK, false, I18nWeb(c, "pages.login.toasts.emptyPassword"))
 		return
 	}
+	if len(form.Username) < 3 || len(form.Username) > 64 {
+		pureJsonMsg(c, http.StatusOK, false, I18nWeb(c, "pages.login.toasts.invalidUsername"))
+		return
+	}
+	if len(form.Password) < 8 || len(form.Password) > 128 {
+		pureJsonMsg(c, http.StatusOK, false, I18nWeb(c, "pages.login.toasts.invalidPassword"))
+		return
+	}
 
 	// Verify Turnstile token if site key is configured
 	turnstileSecretKey, err := a.settingService.GetTurnstileSecretKey()
@@ -154,8 +169,7 @@ func (a *IndexController) register(c *gin.Context) {
 
 	err = a.userService.RegisterUser(form.Username, form.Password, &a.inboundService)
 	if err != nil {
-		errMsg := err.Error()
-		if strings.Contains(errMsg, "already exists") {
+		if errors.Is(err, service.ErrUsernameAlreadyExists) {
 			pureJsonMsg(c, http.StatusOK, false, I18nWeb(c, "pages.login.toasts.userExists"))
 			return
 		}
diff --git a/web/entity/entity.go b/web/entity/entity.go
index dce37800..84f4272b 100644
--- a/web/entity/entity.go
+++ b/web/entity/entity.go
@@ -106,7 +106,7 @@ type AllSetting struct {
 
 	// Registration settings
 	TurnstileSiteKey   string `json:"turnstileSiteKey" form:"turnstileSiteKey"`
-	TurnstileSecretKey string `json:"turnstileSecretKey" form:"turnstileSecretKey"`
+	TurnstileSecretKey string `json:"-" form:"-"` // server-side only, never sent to frontend
 }
 
 // CheckValid validates all settings in the AllSetting struct, checking IP addresses, ports, SSL certificates, and other configuration values.
diff --git a/web/middleware/ratelimit.go b/web/middleware/ratelimit.go
new file mode 100644
index 00000000..99396766
--- /dev/null
+++ b/web/middleware/ratelimit.go
@@ -0,0 +1,82 @@
+package middleware
+
+import (
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/mhsanaei/3x-ui/v2/web/entity"
+)
+
+type rateEntry struct {
+	count    int
+	lastSeen time.Time
+}
+
+// RateLimitMiddleware returns a Gin middleware that limits requests per IP.
+// maxRequests is the maximum number of requests allowed within the window.
+func RateLimitMiddleware(maxRequests int, window time.Duration) gin.HandlerFunc {
+	var mu sync.Mutex
+	entries := make(map[string]*rateEntry)
+
+	// Periodically evict stale entries to prevent unbounded memory growth
+	go func() {
+		ticker := time.NewTicker(window)
+		defer ticker.Stop()
+		for range ticker.C {
+			mu.Lock()
+			cutoff := time.Now().Add(-window * 2)
+			for ip, e := range entries {
+				if e.lastSeen.Before(cutoff) {
+					delete(entries, ip)
+				}
+			}
+			mu.Unlock()
+		}
+	}()
+
+	return func(c *gin.Context) {
+		ip := c.GetHeader("X-Real-IP")
+		if ip == "" {
+			ip = c.GetHeader("X-Forwarded-For")
+			if ip != "" {
+				// Take the first IP from X-Forwarded-For
+				if idx := len(ip); idx > 0 {
+					for i, ch := range ip {
+						if ch == ',' {
+							ip = ip[:i]
+							break
+						}
+					}
+				}
+			}
+		}
+		if ip == "" {
+			ip = c.Request.RemoteAddr
+		}
+
+		mu.Lock()
+		now := time.Now()
+		e, exists := entries[ip]
+		if !exists || now.Sub(e.lastSeen) > window {
+			entries[ip] = &rateEntry{count: 1, lastSeen: now}
+			mu.Unlock()
+			c.Next()
+			return
+		}
+		e.lastSeen = now
+		e.count++
+		if e.count > maxRequests {
+			mu.Unlock()
+			c.JSON(http.StatusTooManyRequests, entity.Msg{
+				Success: false,
+				Msg:     "Too many requests",
+			})
+			c.Abort()
+			return
+		}
+		mu.Unlock()
+		c.Next()
+	}
+}
diff --git a/web/service/setting.go b/web/service/setting.go
index 651b9231..d8792bcc 100644
--- a/web/service/setting.go
+++ b/web/service/setting.go
@@ -959,6 +959,10 @@ func (s *SettingService) GetTurnstileSecretKey() (string, error) {
 	return s.getString("turnstileSecretKey")
 }
 
+func (s *SettingService) SetTurnstileSecretKey(value string) error {
+	return s.setString("turnstileSecretKey", value)
+}
+
 func (s *SettingService) UpdateAllSetting(allSetting *entity.AllSetting) error {
 	if err := allSetting.CheckValid(); err != nil {
 		return err
@@ -974,6 +978,9 @@ func (s *SettingService) UpdateAllSetting(allSetting *entity.AllSetting) error {
 	fields := reflect_util.GetFields(t)
 	for _, field := range fields {
 		key := field.Tag.Get("json")
+		if key == "-" || key == "" {
+			continue
+		}
 		fieldV := v.FieldByName(field.Name)
 		settings[key] = fmt.Sprint(fieldV.Interface())
 	}
diff --git a/web/service/turnstile.go b/web/service/turnstile.go
index 34d0c455..ff93f530 100644
--- a/web/service/turnstile.go
+++ b/web/service/turnstile.go
@@ -6,10 +6,14 @@ import (
 	"net/http"
 	"net/url"
 	"time"
+
+	"github.com/mhsanaei/3x-ui/v2/logger"
 )
 
 const turnstileVerifyURL = "https://challenges.cloudflare.com/turnstile/v0/siteverify"
 
+var turnstileClient = &http.Client{Timeout: 10 * time.Second}
+
 type turnstileResponse struct {
 	Success bool `json:"success"`
 }
@@ -24,20 +28,22 @@ func VerifyTurnstile(secretKey, token, remoteIP string) bool {
 		form.Set("remoteip", remoteIP)
 	}
 
-	client := &http.Client{Timeout: 10 * time.Second}
-	resp, err := client.PostForm(turnstileVerifyURL, form)
+	resp, err := turnstileClient.PostForm(turnstileVerifyURL, form)
 	if err != nil {
+		logger.Warning("Turnstile verification request failed (network error):", err)
 		return false
 	}
 	defer resp.Body.Close()
 
-	body, err := io.ReadAll(resp.Body)
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 4096))
 	if err != nil {
+		logger.Warning("Turnstile verification failed to read response:", err)
 		return false
 	}
 
 	var result turnstileResponse
 	if err := json.Unmarshal(body, &result); err != nil {
+		logger.Warning("Turnstile verification failed to parse response:", err)
 		return false
 	}
 	return result.Success
diff --git a/web/service/user.go b/web/service/user.go
index 7afbc3d5..072e0345 100644
--- a/web/service/user.go
+++ b/web/service/user.go
@@ -15,6 +15,9 @@ import (
 	"gorm.io/gorm"
 )
 
+// ErrUsernameAlreadyExists is returned when a user tries to register with a taken username.
+var ErrUsernameAlreadyExists = errors.New("username already exists")
+
 // UserService provides business logic for user management and authentication.
 // It handles user creation, login, password management, and 2FA operations.
 type UserService struct {
@@ -152,8 +155,9 @@ func (s *UserService) RegisterUser(username string, password string, inboundServ
 			Role:     "user",
 		}
 		if err := tx.Create(user).Error; err != nil {
-			if strings.Contains(err.Error(), "UNIQUE constraint failed") || strings.Contains(err.Error(), "Duplicate") {
-				return errors.New("username already exists")
+			errMsg := err.Error()
+			if strings.Contains(errMsg, "UNIQUE constraint failed") || strings.Contains(errMsg, "Duplicate") {
+				return ErrUsernameAlreadyExists
 			}
 			return err
 		}
diff --git a/web/translation/translate.ar_EG.toml b/web/translation/translate.ar_EG.toml
index c69fa7a0..4aa76642 100644
--- a/web/translation/translate.ar_EG.toml
+++ b/web/translation/translate.ar_EG.toml
@@ -111,6 +111,8 @@
 "successRegister" = "تم التسجيل بنجاح، يرجى تسجيل الدخول."
 "userExists" = "اسم المستخدم موجود بالفعل"
 "errorRegister" = "فشل التسجيل"
+"invalidUsername" = "يجب أن يكون اسم المستخدم بين 3 و 64 حرفًا"
+"invalidPassword" = "يجب أن تكون كلمة المرور بين 8 و 128 حرفًا"
 
 [pages.index]
 "title" = "نظرة عامة"
diff --git a/web/translation/translate.en_US.toml b/web/translation/translate.en_US.toml
index a60766c9..3a9c62d4 100644
--- a/web/translation/translate.en_US.toml
+++ b/web/translation/translate.en_US.toml
@@ -116,6 +116,8 @@
 "successRegister" = "Registration successful, please log in."
 "userExists" = "Username already exists"
 "errorRegister" = "Registration failed"
+"invalidUsername" = "Username must be 3-64 characters"
+"invalidPassword" = "Password must be 8-128 characters"
 
 [pages.index]
 "title" = "Overview"
diff --git a/web/translation/translate.es_ES.toml b/web/translation/translate.es_ES.toml
index e407a0bb..06247d67 100644
--- a/web/translation/translate.es_ES.toml
+++ b/web/translation/translate.es_ES.toml
@@ -111,6 +111,8 @@
 "successRegister" = "Registro exitoso, por favor inicia sesión."
 "userExists" = "El nombre de usuario ya existe"
 "errorRegister" = "Error en el registro"
+"invalidUsername" = "El nombre de usuario debe tener entre 3 y 64 caracteres"
+"invalidPassword" = "La contraseña debe tener entre 8 y 128 caracteres"
 
 [pages.index]
 "title" = "Estado del Sistema"
diff --git a/web/translation/translate.fa_IR.toml b/web/translation/translate.fa_IR.toml
index b21b2c32..94a5e86e 100644
--- a/web/translation/translate.fa_IR.toml
+++ b/web/translation/translate.fa_IR.toml
@@ -111,6 +111,8 @@
 "successRegister" = "ثبت‌نام با موفقیت انجام شد، لطفاً وارد شوید."
 "userExists" = "نام کاربری از قبل وجود دارد"
 "errorRegister" = "ثبت نام ناموفق بود"
+"invalidUsername" = "نام کاربری باید بین ۳ تا ۶۴ کاراکتر باشد"
+"invalidPassword" = "رمز عبور باید بین ۸ تا ۱۲۸ کاراکتر باشد"
 
 [pages.index]
 "title" = "نمای کلی"
diff --git a/web/translation/translate.id_ID.toml b/web/translation/translate.id_ID.toml
index edb3fb95..d345403f 100644
--- a/web/translation/translate.id_ID.toml
+++ b/web/translation/translate.id_ID.toml
@@ -111,6 +111,8 @@
 "successRegister" = "Pendaftaran berhasil, silakan masuk."
 "userExists" = "Nama pengguna sudah ada"
 "errorRegister" = "Pendaftaran gagal"
+"invalidUsername" = "Nama pengguna harus 3-64 karakter"
+"invalidPassword" = "Kata sandi harus 8-128 karakter"
 
 [pages.index]
 "title" = "Ikhtisar"
diff --git a/web/translation/translate.ja_JP.toml b/web/translation/translate.ja_JP.toml
index 3bddb7c1..a4936bbb 100644
--- a/web/translation/translate.ja_JP.toml
+++ b/web/translation/translate.ja_JP.toml
@@ -111,6 +111,8 @@
 "successRegister" = "登録が完了しました。ログインしてください。"
 "userExists" = "ユーザー名は既に存在します"
 "errorRegister" = "登録に失敗しました"
+"invalidUsername" = "ユーザー名は3〜64文字で入力してください"
+"invalidPassword" = "パスワードは8〜128文字で入力してください"
 
 [pages.index]
 "title" = "システムステータス"
diff --git a/web/translation/translate.pt_BR.toml b/web/translation/translate.pt_BR.toml
index 6f876359..77bbd9a8 100644
--- a/web/translation/translate.pt_BR.toml
+++ b/web/translation/translate.pt_BR.toml
@@ -111,6 +111,8 @@
 "successRegister" = "Registro bem-sucedido, por favor faça login."
 "userExists" = "Nome de usuário já existe"
 "errorRegister" = "Falha no registro"
+"invalidUsername" = "O nome de usuário deve ter entre 3 e 64 caracteres"
+"invalidPassword" = "A senha deve ter entre 8 e 128 caracteres"
 
 [pages.index]
 "title" = "Visão Geral"
diff --git a/web/translation/translate.ru_RU.toml b/web/translation/translate.ru_RU.toml
index a973a0d2..ed544bbb 100644
--- a/web/translation/translate.ru_RU.toml
+++ b/web/translation/translate.ru_RU.toml
@@ -111,6 +111,8 @@
 "successRegister" = "Регистрация прошла успешно, пожалуйста, войдите."
 "userExists" = "Имя пользователя уже существует"
 "errorRegister" = "Ошибка регистрации"
+"invalidUsername" = "Имя пользователя должно содержать от 3 до 64 символов"
+"invalidPassword" = "Пароль должен содержать от 8 до 128 символов"
 
 [pages.index]
 "title" = "Дашборд"
diff --git a/web/translation/translate.tr_TR.toml b/web/translation/translate.tr_TR.toml
index b510a686..a1857a2a 100644
--- a/web/translation/translate.tr_TR.toml
+++ b/web/translation/translate.tr_TR.toml
@@ -111,6 +111,8 @@
 "successRegister" = "Kayıt başarılı, lütfen giriş yapın."
 "userExists" = "Kullanıcı adı zaten mevcut"
 "errorRegister" = "Kayıt başarısız"
+"invalidUsername" = "Kullanıcı adı 3-64 karakter olmalıdır"
+"invalidPassword" = "Şifre 8-128 karakter olmalıdır"
 
 [pages.index]
 "title" = "Genel Bakış"
diff --git a/web/translation/translate.uk_UA.toml b/web/translation/translate.uk_UA.toml
index 6e42d2aa..a7735af7 100644
--- a/web/translation/translate.uk_UA.toml
+++ b/web/translation/translate.uk_UA.toml
@@ -111,6 +111,8 @@
 "successRegister" = "Реєстрація пройшла успішно, будь ласка, увійдіть."
 "userExists" = "Ім'я користувача вже існує"
 "errorRegister" = "Помилка реєстрації"
+"invalidUsername" = "Ім'я користувача повинно містити від 3 до 64 символів"
+"invalidPassword" = "Пароль повинен містити від 8 до 128 символів"
 
 [pages.index]
 "title" = "Огляд"
diff --git a/web/translation/translate.vi_VN.toml b/web/translation/translate.vi_VN.toml
index b2a54800..c37c34ca 100644
--- a/web/translation/translate.vi_VN.toml
+++ b/web/translation/translate.vi_VN.toml
@@ -111,6 +111,8 @@
 "successRegister" = "Đăng ký thành công, vui lòng đăng nhập."
 "userExists" = "Tên người dùng đã tồn tại"
 "errorRegister" = "Đăng ký thất bại"
+"invalidUsername" = "Tên người dùng phải từ 3-64 ký tự"
+"invalidPassword" = "Mật khẩu phải từ 8-128 ký tự"
 
 [pages.index]
 "title" = "Trạng thái hệ thống"
diff --git a/web/translation/translate.zh_CN.toml b/web/translation/translate.zh_CN.toml
index e8e02d5c..3252dcf6 100644
--- a/web/translation/translate.zh_CN.toml
+++ b/web/translation/translate.zh_CN.toml
@@ -116,6 +116,8 @@
 "successRegister" = "注册成功，请登录。"
 "userExists" = "用户名已存在"
 "errorRegister" = "注册失败"
+"invalidUsername" = "用户名长度必须为3-64个字符"
+"invalidPassword" = "密码长度必须为8-128个字符"
 
 [pages.index]
 "title" = "系统状态"
diff --git a/web/translation/translate.zh_TW.toml b/web/translation/translate.zh_TW.toml
index f2fb4539..9000c73d 100644
--- a/web/translation/translate.zh_TW.toml
+++ b/web/translation/translate.zh_TW.toml
@@ -111,6 +111,8 @@
 "successRegister" = "註冊成功，請登入。"
 "userExists" = "使用者名稱已存在"
 "errorRegister" = "註冊失敗"
+"invalidUsername" = "使用者名稱長度必須為3-64個字元"
+"invalidPassword" = "密碼長度必須為8-128個字元"
 
 [pages.index]
 "title" = "系統狀態"