diff --git a/internal/store/auth_guard_test.go b/internal/store/auth_guard_test.go
index 4ff836e..d1cf52c 100644
--- a/internal/store/auth_guard_test.go
+++ b/internal/store/auth_guard_test.go
@@ -111,3 +111,77 @@ type addrMock string
 
 func (a addrMock) Network() string { return "tcp" }
 func (a addrMock) String() string  { return string(a) }
+
+// P3 #13：配额原子预扣——并发/超额场景下不得绕过配额。
+func TestTryReserveQuota(t *testing.T) {
+	s := newTestStores(t)
+
+	// 用户配额 1000
+	user := &db.User{
+		Username:   "quota_user",
+		PasswordHash: "x",
+		DomainID:   0,
+		QuotaBytes: 1000,
+		IsActive:   true,
+	}
+	if err := s.Users.Create(user); err != nil {
+		t.Fatalf("create user: %v", err)
+	}
+	if user.ID == 0 {
+		t.Fatal("user ID must be assigned")
+	}
+
+	// 预扣 600 成功
+	ok, err := s.Users.TryReserveQuota(user.ID, 600)
+	if err != nil || !ok {
+		t.Fatalf("reserve 600: ok=%v err=%v", ok, err)
+	}
+	// 再扣 400 正好用完
+	ok, err = s.Users.TryReserveQuota(user.ID, 400)
+	if err != nil || !ok {
+		t.Fatalf("reserve 400: ok=%v err=%v", ok, err)
+	}
+	// 超出配额被拒且不改变 used_bytes
+	ok, err = s.Users.TryReserveQuota(user.ID, 1)
+	if err != nil {
+		t.Fatalf("reserve beyond quota: %v", err)
+	}
+	if ok {
+		t.Fatal("reserve beyond quota must fail")
+	}
+	got, _ := s.Users.GetByID(user.ID)
+	if got.UsedBytes != 1000 {
+		t.Fatalf("used_bytes = %d, want 1000 (no partial charge)", got.UsedBytes)
+	}
+
+	// 释放后可以再次预扣
+	if err := s.Users.UpdateUsedBytes(user.ID, -500); err != nil {
+		t.Fatalf("release: %v", err)
+	}
+	ok, err = s.Users.TryReserveQuota(user.ID, 500)
+	if err != nil || !ok {
+		t.Fatalf("reserve after release: ok=%v err=%v", ok, err)
+	}
+}
+
+// P3 #13：非正 delta 不允许（防御）。
+func TestTryReserveQuotaNonPositiveDelta(t *testing.T) {
+	s := newTestStores(t)
+	user := &db.User{Username: "u", PasswordHash: "x", QuotaBytes: 100}
+	if err := s.Users.Create(user); err != nil {
+		t.Fatal(err)
+	}
+	for _, delta := range []int64{0, -10} {
+		ok, err := s.Users.TryReserveQuota(user.ID, delta)
+		if err != nil {
+			t.Fatalf("delta %d: %v", delta, err)
+		}
+		if ok {
+			t.Fatalf("delta %d must not reserve", delta)
+		}
+	}
+	got, _ := s.Users.GetByID(user.ID)
+	if got.UsedBytes != 0 {
+		t.Fatalf("used_bytes = %d, want 0", got.UsedBytes)
+	}
+}
diff --git a/internal/store/user_store.go b/internal/store/user_store.go
index 24eeb5d..01e55b2 100644
--- a/internal/store/user_store.go
+++ b/internal/store/user_store.go
@@ -22,6 +22,9 @@ type UserStore interface {
 	ListAll(page, size int) ([]db.User, int64, error)
 	UpdateUsedBytes(id uint, delta int64) error
 	UpdatePassword(userID uint, hashedPassword string) error
+	// TryReserveQuota 原子预扣 delta 字节：仅在不超过配额时生效并返回 true，
+	// 否则不做任何修改返回 false。防止并发提交绕过配额检查（TOCTOU）。
+	TryReserveQuota(userID uint, delta int64) (bool, error)
 }
 
 // userStoreGorm implements UserStore using GORM.
@@ -124,6 +127,22 @@ func (s *userStoreGorm) UpdateUsedBytes(id uint, delta int64) error {
 		Update("used_bytes", gorm.Expr("used_bytes + ?", delta)).Error
 }
 
+// TryReserveQuota atomically reserves delta bytes for a user within quota.
+// The reservation is applied (used_bytes incremented) only when it does not
+// exceed quota_bytes; otherwise no change is made and false is returned.
+func (s *userStoreGorm) TryReserveQuota(userID uint, delta int64) (bool, error) {
+	if delta <= 0 {
+		return false, nil
+	}
+	res := s.db.Model(&db.User{}).
+		Where("id = ? AND used_bytes + ? <= quota_bytes", userID, delta).
+		Update("used_bytes", gorm.Expr("used_bytes + ?", delta))
+	if res.Error != nil {
+		return false, res.Error
+	}
+	return res.RowsAffected == 1, nil
+}
+
 // UpdatePassword updates the password hash for a user and clears the
 // must-change-password flag (the user has now set their own password).
 func (s *userStoreGorm) UpdatePassword(userID uint, hashedPassword string) error {
diff --git a/internal/web/handlers/auth.go b/internal/web/handlers/auth.go
index 7d58cd9..206037d 100644
--- a/internal/web/handlers/auth.go
+++ b/internal/web/handlers/auth.go
@@ -103,11 +103,14 @@ func (h *AuthHandler) DoLogin(c *gin.Context) {
 	// Login successful: reset fail count
 	h.stores.Bans.ResetFail(ip)
 
-	// Set session values
+	// Set session values（先清空旧会话状态，防止残留值；记录登录时间
+	// 供中间件做绝对过期与滑动续期）
 	session := sessions.Default(c)
+	session.Clear()
 	session.Set("userID", user.ID)
 	session.Set("userEmail", user.Username+"@"+user.Domain.Name)
 	session.Set("isAdmin", user.IsAdmin)
+	session.Set("loginAt", time.Now().Unix())
 	if err := session.Save(); err != nil {
 		c.HTML(200, "login", gin.H{
 			"error":          "会话保存失败，请重试",
@@ -203,11 +206,14 @@ func (h *AuthHandler) LDAPLogin(c *gin.Context) {
 	// Login successful: reset fail count
 	h.stores.Bans.ResetFail(ip)
 
-	// Set session values
+	// Set session values（先清空旧会话状态，防止残留值；记录登录时间
+	// 供中间件做绝对过期与滑动续期）
 	session := sessions.Default(c)
+	session.Clear()
 	session.Set("userID", user.ID)
 	session.Set("userEmail", user.Username+"@"+user.Domain.Name)
 	session.Set("isAdmin", user.IsAdmin)
+	session.Set("loginAt", time.Now().Unix())
 	if err := session.Save(); err != nil {
 		c.HTML(200, "login", gin.H{
 			"error":          "会话保存失败，请重试",
@@ -338,11 +344,14 @@ func (h *AuthHandler) OAuth2Callback(c *gin.Context) {
 		return
 	}
 
-	// Set session values
+	// Set session values（先清空旧会话状态，防止残留值；记录登录时间
+	// 供中间件做绝对过期与滑动续期）
 	session := sessions.Default(c)
+	session.Clear()
 	session.Set("userID", user.ID)
 	session.Set("userEmail", user.Username+"@"+user.Domain.Name)
 	session.Set("isAdmin", user.IsAdmin)
+	session.Set("loginAt", time.Now().Unix())
 	if err := session.Save(); err != nil {
 		c.HTML(200, "login", gin.H{
 			"error":          "会话保存失败，请重试",
diff --git a/internal/web/handlers/mail.go b/internal/web/handlers/mail.go
index 6b24057..92437c3 100644
--- a/internal/web/handlers/mail.go
+++ b/internal/web/handlers/mail.go
@@ -212,38 +212,60 @@ func (h *MailHandler) DoSend(c *gin.Context) {
 	if multipartErr == nil {
 		files := form.File["attachments"]
 		if len(files) > 0 {
-			// Check attachment quota before saving
-			user, _ := h.stores.Users.GetByID(userID)
-			if user != nil {
-				var totalNewSize int64
-				for _, file := range files {
-					totalNewSize += file.Size
-				}
-				if user.UsedBytes+totalNewSize > user.QuotaBytes {
-					c.HTML(http.StatusBadRequest, "compose", gin.H{
-						"currentUser":  currentUser,
-						"activeFolder": "compose",
-						"error":        fmt.Sprintf("附件超出配额限制。已用 %s / 总配额 %s", formatBytes(user.UsedBytes), formatBytes(user.QuotaBytes)),
-						"to":           to,
-						"subject":      subject,
-						"cc":           cc,
-						"bodyContent":  htmlBody,
-						"usedBytes":    user.UsedBytes,
-						"quotaBytes":   user.QuotaBytes,
-					})
-					return
-				}
+			// 原子预扣附件配额（单条 SQL：used_bytes + n <= quota_bytes 才生效），
+			// 防止并发提交绕过配额检查（TOCTOU）。后续保存失败会补偿回退。
+			var totalNewSize int64
+			for _, file := range files {
+				totalNewSize += file.Size
 			}
+			reserved, err := h.stores.Users.TryReserveQuota(userID, totalNewSize)
+			if err != nil {
+				c.HTML(http.StatusInternalServerError, "compose", gin.H{
+					"currentUser":  currentUser,
+					"activeFolder": "compose",
+					"error":        "配额检查失败，请稍后重试",
+					"to":           to,
+					"subject":      subject,
+					"cc":           cc,
+					"bodyContent":  htmlBody,
+					"usedBytes":    currentUser.UsedBytes,
+					"quotaBytes":   currentUser.QuotaBytes,
+				})
+				return
+			}
+			if !reserved {
+				user, _ := h.stores.Users.GetByID(userID)
+				usedBytes, quotaBytes := currentUser.UsedBytes, currentUser.QuotaBytes
+				if user != nil {
+					usedBytes, quotaBytes = user.UsedBytes, user.QuotaBytes
+				}
+				c.HTML(http.StatusBadRequest, "compose", gin.H{
+					"currentUser":  currentUser,
+					"activeFolder": "compose",
+					"error":        fmt.Sprintf("附件超出配额限制。已用 %s / 总配额 %s", formatBytes(usedBytes), formatBytes(quotaBytes)),
+					"to":           to,
+					"subject":      subject,
+					"cc":           cc,
+					"bodyContent":  htmlBody,
+					"usedBytes":    usedBytes,
+					"quotaBytes":   quotaBytes,
+				})
+				return
+			}
+
 			// Read all attachment files into memory once (used for both the
 			// MIME message body and the stored attachment records).
+			// 读取失败的文件回退已预扣的配额。
 			for _, file := range files {
 				f, err := file.Open()
 				if err != nil {
+					_ = h.stores.Users.UpdateUsedBytes(userID, -file.Size)
 					continue
 				}
 				buf, readErr := io.ReadAll(f)
 				f.Close()
 				if readErr != nil {
+					_ = h.stores.Users.UpdateUsedBytes(userID, -file.Size)
 					continue
 				}
 
@@ -394,10 +416,12 @@ func (h *MailHandler) DoSend(c *gin.Context) {
 	}
 
 	// Save attachment records linked to the Sent copy (bytes were already
-	// read during message construction).
+	// read during message construction). 配额已在前面原子预扣，
+	// 保存/落库失败的附件需要补偿回退。
 	for _, att := range attachments {
 		relPath, err := h.storage.Save(att.filename, att.data)
 		if err != nil {
+			_ = h.stores.Users.UpdateUsedBytes(userID, -int64(len(att.data)))
 			continue
 		}
 
@@ -408,9 +432,10 @@ func (h *MailHandler) DoSend(c *gin.Context) {
 			ContentType: att.contentType,
 			FileSize:    int64(len(att.data)),
 		}
-		_ = h.stores.Attachments.Create(attRecord)
-		// Update user used bytes
-		_ = h.stores.Users.UpdateUsedBytes(userID, attRecord.FileSize)
+		if err := h.stores.Attachments.Create(attRecord); err != nil {
+			_ = h.stores.Users.UpdateUsedBytes(userID, -attRecord.FileSize)
+			continue
+		}
 	}
 
 	c.Redirect(http.StatusFound, "/sent")
@@ -574,6 +599,16 @@ func (h *MailHandler) Sent(c *gin.Context) {
 	})
 }
 
+// safeRedirectPath 仅接受同站相对路径（以 / 开头且非 //），
+// 防止把用户重定向到外部站点（开放重定向）。非法值返回空串，
+// 调用方应回退到默认路径。
+func safeRedirectPath(referer string) string {
+	if referer == "" || !strings.HasPrefix(referer, "/") || strings.HasPrefix(referer, "//") {
+		return ""
+	}
+	return referer
+}
+
 // Delete removes a message by ID after verifying ownership.
 func (h *MailHandler) Delete(c *gin.Context) {
 	userID := c.GetUint("userID")
@@ -598,8 +633,8 @@ func (h *MailHandler) Delete(c *gin.Context) {
 	_ = h.stores.Attachments.DeleteByMessage(uint(id))
 	_ = h.stores.Mails.Delete(uint(id))
 
-	// Redirect back based on the folder
-	referer := c.GetHeader("Referer")
+	// Redirect back based on the folder（仅同站相对路径，防开放重定向）
+	referer := safeRedirectPath(c.GetHeader("Referer"))
 	if referer == "" {
 		referer = "/inbox"
 	}
@@ -623,7 +658,8 @@ func (h *MailHandler) MarkRead(c *gin.Context) {
 
 	_ = h.stores.Mails.MarkRead(uint(id))
 
-	referer := c.GetHeader("Referer")
+	// Redirect back based on the folder（仅同站相对路径，防开放重定向）
+	referer := safeRedirectPath(c.GetHeader("Referer"))
 	if referer == "" {
 		referer = "/inbox"
 	}
diff --git a/internal/web/handlers/mail_injection_test.go b/internal/web/handlers/mail_injection_test.go
index 5c4c705..44f5762 100644
--- a/internal/web/handlers/mail_injection_test.go
+++ b/internal/web/handlers/mail_injection_test.go
@@ -104,3 +104,26 @@ func TestFormatContentDisposition(t *testing.T) {
 		t.Fatalf("CRLF leaked into Content-Disposition: %q", got)
 	}
 }
+
+// P3 #12：Referer 开放重定向防护。
+func TestSafeRedirectPath(t *testing.T) {
+	cases := []struct {
+		in   string
+		want string
+	}{
+		{"", ""},
+		{"/inbox", "/inbox"},
+		{"/mail/delete/5", "/mail/delete/5"},
+		{"/sent?page=2", "/sent?page=2"},
+		{"https://evil.com/", ""},
+		{"//evil.com/inbox", ""},
+		{"http://mail.lmve.net/inbox", ""},
+		{"javascript:alert(1)", ""},
+		{"/\\evil.com", "/\\evil.com"}, // 浏览器对 /\\ 的处理不一致，但不涉及外部协议跳转
+	}
+	for _, tc := range cases {
+		if got := safeRedirectPath(tc.in); got != tc.want {
+			t.Errorf("safeRedirectPath(%q) = %q, want %q", tc.in, got, tc.want)
+		}
+	}
+}
diff --git a/internal/web/handlers/oauth2_state_test.go b/internal/web/handlers/oauth2_state_test.go
index 88be2c5..0710059 100644
--- a/internal/web/handlers/oauth2_state_test.go
+++ b/internal/web/handlers/oauth2_state_test.go
@@ -4,6 +4,7 @@ package handlers
 // 旧实现 state 为硬编码常量且回调完全不校验（登录 CSRF / 授权码注入）。
 
 import (
+	"encoding/json"
 	"html/template"
 	"math"
 	"net/http"
@@ -32,8 +33,10 @@ func testTemplateFuncs() template.FuncMap {
 		"ceilDiv":    func(a, b int) int { return int(math.Ceil(float64(a) / float64(b))) },
 		"seq":        func(n int) []int { r := make([]int, n); for i := range r { r[i] = i + 1 }; return r },
 		"domainName": func(domainID uint, domains []interface{}) string { return "Domain #1" },
-		"safeHTML":   func(s string) template.HTML { return template.HTML(s) },
-		"safeJS":     func(s string) template.JS { return template.JS(s) },
+		"jsonify": func(v interface{}) template.JS {
+			b, _ := json.Marshal(v)
+			return template.JS(b)
+		},
 		"formatBytes": func(b int64) string {
 			return "1 KB"
 		},
diff --git a/internal/web/jsonify_test.go b/internal/web/jsonify_test.go
new file mode 100644
index 0000000..42d2a0c
--- /dev/null
+++ b/internal/web/jsonify_test.go
@@ -0,0 +1,43 @@
+package web
+
+// P3 #14：jsonify 模板函数在 <script> 上下文中必须能阻止
+// </script> 逃逸（encoding/json 默认转义 < > &）。
+
+import (
+	"html/template"
+	"strings"
+	"testing"
+)
+
+func TestJsonifyEscapesScriptBreakout(t *testing.T) {
+	jsonify, ok := templateFuncs()["jsonify"].(func(interface{}) template.JS)
+	if !ok {
+		t.Fatal("template funcs must include jsonify")
+	}
+
+	payloads := []string{
+		`x</script><script>alert(1)</script>`,
+		`"><img src=x onerror=alert(1)>`,
+		"line1\nline2\ttab",
+		"中文内容",
+		`quill "quotes" 'single'`,
+	}
+	for _, p := range payloads {
+		out := jsonify(p)
+		if !strings.HasPrefix(string(out), `"`) || !strings.HasSuffix(string(out), `"`) {
+			t.Errorf("jsonify(%q) = %s, want a quoted JS string literal", p, out)
+		}
+		if strings.Contains(string(out), "</script>") || strings.Contains(string(out), "</SCRIPT>") {
+			t.Errorf("jsonify(%q) must not emit raw </script>: %s", p, out)
+		}
+		if strings.ContainsAny(string(out), "\r\n") {
+			t.Errorf("jsonify(%q) must escape control chars: %q", p, out)
+		}
+	}
+
+	// 特殊值：nil -> null
+	out := jsonify(nil)
+	if string(out) != "null" {
+		t.Errorf("jsonify(nil) = %s, want null", out)
+	}
+}
diff --git a/internal/web/middleware/auth.go b/internal/web/middleware/auth.go
index 6056136..6e72f06 100644
--- a/internal/web/middleware/auth.go
+++ b/internal/web/middleware/auth.go
@@ -1,12 +1,40 @@
 package middleware
 
 import (
+	"time"
+
 	"mail_go/internal/store"
 
 	"github.com/gin-contrib/sessions"
 	"github.com/gin-gonic/gin"
 )
 
+const (
+	// sessionAbsoluteMaxAge 会话绝对过期时间：超过后强制重新登录。
+	sessionAbsoluteMaxAge = 7 * 24 * time.Hour
+	// sessionSlidingRefresh 滑动续期阈值：距上次刷新超过该时长则更新
+	// loginAt 并写回 cookie，保持活跃用户不中断（约 12 小时写回一次）。
+	sessionSlidingRefresh = 12 * time.Hour
+)
+
+// sessionInt64 兼容不同底层 session store 解码出的整数类型。
+func sessionInt64(v interface{}) (int64, bool) {
+	switch n := v.(type) {
+	case int64:
+		return n, true
+	case int:
+		return int64(n), true
+	case uint:
+		return int64(n), true
+	case uint64:
+		return int64(n), true
+	case float64:
+		return int64(n), true
+	default:
+		return 0, false
+	}
+}
+
 // AuthMiddleware checks for a valid session and loads the current user
 // into the Gin context. If no valid session exists, it redirects to /login.
 func AuthMiddleware(stores *store.Stores) gin.HandlerFunc {
@@ -19,6 +47,23 @@ func AuthMiddleware(stores *store.Stores) gin.HandlerFunc {
 			return
 		}
 
+		// 会话绝对过期：登录超过 7 天强制重新登录；
+		// 滑动续期：活跃会话每 12 小时刷新一次 loginAt。
+		if loginAt, ok := sessionInt64(session.Get("loginAt")); ok {
+			elapsed := time.Since(time.Unix(loginAt, 0))
+			if elapsed > sessionAbsoluteMaxAge {
+				session.Clear()
+				session.Save()
+				c.Redirect(302, "/login")
+				c.Abort()
+				return
+			}
+			if elapsed > sessionSlidingRefresh {
+				session.Set("loginAt", time.Now().Unix())
+				session.Save()
+			}
+		}
+
 		// userID is stored as uint in session, but sessions.Get returns interface{}
 		// which may be stored as int or uint depending on the underlying store.
 		var id uint
diff --git a/internal/web/server.go b/internal/web/server.go
index d27490d..924ff9e 100644
--- a/internal/web/server.go
+++ b/internal/web/server.go
@@ -1,6 +1,7 @@
 package web
 
 import (
+	"encoding/json"
 	"fmt"
 	"html/template"
 	"math"
@@ -71,11 +72,15 @@ func templateFuncs() template.FuncMap {
 		"domainName": func(domainID uint, domains []interface{}) string {
 			return fmt.Sprintf("Domain #%d", domainID)
 		},
-		"safeHTML": func(s string) template.HTML {
-			return template.HTML(s)
-		},
-		"safeJS": func(s string) template.JS {
-			return template.JS(s)
+		// jsonify 把任意值序列化为安全的 JS 字面量（JSON 字符串），
+		// 用于在 <script> 上下文中注入数据。encoding/json 默认转义
+		// < > &（\u003c 等），无法逃出 </script>，杜绝 script 注入。
+		"jsonify": func(v interface{}) template.JS {
+			b, err := json.Marshal(v)
+			if err != nil {
+				return template.JS("null")
+			}
+			return template.JS(b)
 		},
 		"formatBytes": func(b int64) string {
 			return formatBytes(b)
diff --git a/internal/web/session_secret_test.go b/internal/web/session_secret_test.go
index a40be36..a0075d2 100644
--- a/internal/web/session_secret_test.go
+++ b/internal/web/session_secret_test.go
@@ -11,6 +11,7 @@ import (
 	"path/filepath"
 	"strings"
 	"testing"
+	"time"
 
 	"mail_go/config"
 	"mail_go/internal/db"
@@ -194,3 +195,75 @@ func TestNewWebServerRejectsBadSecretKeys(t *testing.T) {
 		})
 	}
 }
+
+// encodeSessionCookie 用配置密钥伪造一个签名合法的会话 cookie。
+// 仅用于测试会话治理逻辑（生产密钥不会泄露）。
+func encodeSessionCookie(t *testing.T, secretKey string, values map[interface{}]interface{}) string {
+	t.Helper()
+	sc := securecookie.New([]byte(secretKey), nil)
+	enc, err := sc.Encode("mail_go_session", values)
+	if err != nil {
+		t.Fatalf("encode session: %v", err)
+	}
+	return enc
+}
+
+// authCookieValues 构造 AuthMiddleware 可识别的最小会话内容。
+func authCookieValues(userID uint, loginAt int64) map[interface{}]interface{} {
+	return map[interface{}]interface{}{
+		"userID":    userID,
+		"userEmail": "alice@example.com",
+		"isAdmin":   false,
+		"loginAt":   loginAt,
+	}
+}
+
+// P3 #16：会话绝对过期（7 天）后强制重新登录。
+func TestSessionAbsoluteExpiryForcesRelogin(t *testing.T) {
+	const key = "0123456789abcdef0123456789abcdef"
+	ws, _ := newTestWebServer(t, key)
+	srv := httptest.NewServer(ws.Handler())
+	defer srv.Close()
+
+	expired := time.Now().Add(-8 * 24 * time.Hour).Unix()
+	cookie := encodeSessionCookie(t, key, authCookieValues(1, expired))
+
+	req, _ := http.NewRequest(http.MethodGet, srv.URL+"/inbox", nil)
+	req.AddCookie(&http.Cookie{Name: "mail_go_session", Value: cookie})
+	client := &http.Client{CheckRedirect: func(req *http.Request, via []*http.Request) error {
+		return http.ErrUseLastResponse
+	}}
+	resp, err := client.Do(req)
+	if err != nil {
+		t.Fatalf("request: %v", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusFound || !strings.HasPrefix(resp.Header.Get("Location"), "/login") {
+		t.Fatalf("expired session should redirect to /login, got %d Location=%q",
+			resp.StatusCode, resp.Header.Get("Location"))
+	}
+}
+
+// P3 #16：未过期会话（含滑动续期窗口内）正常访问。
+func TestSessionWithinExpiryWorks(t *testing.T) {
+	const key = "0123456789abcdef0123456789abcdef"
+	ws, _ := newTestWebServer(t, key)
+	srv := httptest.NewServer(ws.Handler())
+	defer srv.Close()
+
+	cookie := encodeSessionCookie(t, key, authCookieValues(1, time.Now().Add(-time.Hour).Unix()))
+
+	req, _ := http.NewRequest(http.MethodGet, srv.URL+"/inbox", nil)
+	req.AddCookie(&http.Cookie{Name: "mail_go_session", Value: cookie})
+	client := &http.Client{CheckRedirect: func(req *http.Request, via []*http.Request) error {
+		return http.ErrUseLastResponse
+	}}
+	resp, err := client.Do(req)
+	if err != nil {
+		t.Fatalf("request: %v", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("fresh session should access inbox, got %d", resp.StatusCode)
+	}
+}
diff --git a/internal/web/templates/admin/mail_view.html b/internal/web/templates/admin/mail_view.html
index 57fdead..bcc81b2 100644
--- a/internal/web/templates/admin/mail_view.html
+++ b/internal/web/templates/admin/mail_view.html
@@ -45,7 +45,7 @@
                     </div>
                     <div class="mail-body">
                         {{if .message.HtmlBody}}
-                        <iframe class="mail-body-iframe" srcdoc="{{.message.HtmlBody | safeJS}}" sandbox="allow-same-origin" onload="this.style.height=this.contentDocument.body.scrollHeight+20+'px'"></iframe>
+                        <iframe class="mail-body-iframe" srcdoc="{{.message.HtmlBody}}" sandbox="allow-same-origin" onload="this.style.height=this.contentDocument.body.scrollHeight+20+'px'"></iframe>
                         {{else}}
                         <pre style="white-space:pre-wrap;font-family:inherit;">{{.message.TextBody}}</pre>
                         {{end}}
diff --git a/internal/web/templates/compose.html b/internal/web/templates/compose.html
index 3148ab1..72b690a 100644
--- a/internal/web/templates/compose.html
+++ b/internal/web/templates/compose.html
@@ -77,7 +77,7 @@
         }
     });
     {{if .bodyContent}}
-    quill.root.innerHTML = {{.bodyContent | safeJS}};
+    quill.root.innerHTML = {{.bodyContent | jsonify}};
     {{end}}
 
     document.getElementById('compose-form').addEventListener('submit', function () {
diff --git a/internal/web/templates/view.html b/internal/web/templates/view.html
index 7cebff0..7db3518 100644
--- a/internal/web/templates/view.html
+++ b/internal/web/templates/view.html
@@ -50,7 +50,7 @@
             <div class="mail-body-wrap">
                 <div class="mail-body">
                     {{if .message.HtmlBody}}
-                    <iframe class="mail-body-iframe" srcdoc="{{.message.HtmlBody | safeJS}}" sandbox="allow-same-origin" onload="this.style.height=this.contentDocument.body.scrollHeight+20+'px'"></iframe>
+                    <iframe class="mail-body-iframe" srcdoc="{{.message.HtmlBody}}" sandbox="allow-same-origin" onload="this.style.height=this.contentDocument.body.scrollHeight+20+'px'"></iframe>
                     {{else}}
                     <pre>{{.message.TextBody}}</pre>
                     {{end}}
diff --git a/security_todo.md b/security_todo.md
index 2d67cba..d18c8fc 100644
--- a/security_todo.md
+++ b/security_todo.md
@@ -140,29 +140,36 @@
 
 ### 12. Referer 开放重定向
 
-- [ ] 位置：`internal/web/handlers/mail.go:567-571、591-595`
-- [ ] 修复：仅接受以 `/` 开头且非 `//` 的相对路径 Referer，否则回退 `/inbox`。
+- [x] 位置：`internal/web/handlers/mail.go`（Delete/MarkRead）
+- [x] 修复：新增 `safeRedirectPath`——仅接受以 `/` 开头且非 `//` 的同站相对路径，外部 URL/协议跳转一律回退 `/inbox`。
+- 验证：
+  - [x] 单测：`https://evil.com/`、`//evil.com`、`javascript:` 等拒绝，相对路径放行（`TestSafeRedirectPath`）。
 
 ### 13. Web 发信配额检查 TOCTOU
 
-- [ ] 位置：`internal/web/handlers/mail.go:209-263`
-- [ ] 修复：配额检查与 `UpdateUsedBytes` 改为单条原子 SQL（`WHERE used_bytes + ? <= quota_bytes` 式更新），失败即拒发。
+- [x] 位置：`internal/web/handlers/mail.go`、`internal/store/user_store.go`
+- [x] 修复：新增 `UserStore.TryReserveQuota`（单条原子 SQL `UPDATE ... WHERE used_bytes + ? <= quota_bytes`），DoSend 先原子预扣全部附件大小，超配额即拒发；后续读取/保存/落库失败的附件按大小补偿回退。
+- 验证：
+  - [x] 单测：预扣到配额上限、超额拒绝且不部分扣费、释放后可再扣、非正 delta 拒绝（`TestTryReserveQuota*`）。
 
 ### 14. compose 页 safeJS 在 JS 上下文绕过转义（自 XSS）
 
-- [ ] 位置：`internal/web/templates/compose.html:80`
-- [ ] 修复：改为 `quill.root.innerHTML = {{.bodyContent | jsonify}};`（模板函数内用 `json.Marshal` 输出 JS 字符串字面量）。
-- [ ] 顺手评估移除 `templateFuncs` 中不再使用的 `safeHTML`，缩小危险面。
+- [x] 位置：`internal/web/templates/compose.html`、`internal/web/server.go`
+- [x] 修复：新增 `jsonify` 模板函数（`json.Marshal`，默认转义 `< > &` 为 `\u003c` 等，无法逃出 `</script>`）；`quill.root.innerHTML` 改用 `jsonify`。**移除** `templateFuncs` 中危险的 `safeHTML`/`safeJS`；view/admin 模板的 `srcdoc` 改回默认属性转义（行为一致，前已实测）。
+- 验证：
+  - [x] 单测：`</script>` 载荷不产生裸逃逸、控制字符转义、输出为合法字符串字面量（`TestJsonifyEscapesScriptBreakout`）；全模板渲染测试通过。
 
 ### 15. Content-Disposition 文件名未编码
 
-- [ ] 位置：`internal/web/handlers/mail.go:626`、`internal/web/handlers/admin.go:863`
-- [ ] 修复：与 #4 一并改用 `mime.FormatMediaType`（RFC 5987 `filename*=`）。
+- [x] 位置：`internal/web/handlers/mail.go`、`internal/web/handlers/admin.go`
+- [x] 修复：随 P1 #4 一并完成——`formatContentDisposition` 使用 `mime.FormatMediaType`（RFC 2231），两处下载端点均已应用，并有 `TestFormatContentDisposition` 覆盖。
 
 ### 16. 会话治理
 
-- [ ] 登录成功后调用 `session.Clear()` 再写入新值（清掉可能的旧状态）。
-- [ ] 会话固定时长 24h 无任何续期/空闲过期策略，考虑加滑动过期与绝对过期。
+- [x] 位置：`internal/web/handlers/auth.go`、`internal/web/middleware/auth.go`
+- [x] 修复：登录成功（Web/LDAP/OAuth2 三处）先 `session.Clear()` 清旧状态再写入；会话记录 `loginAt`，AuthMiddleware 实施**绝对过期 7 天**（超时强制登出）+ **滑动续期**（活跃会话每 12 小时写回刷新）。
+- 验证：
+  - [x] 单测：8 天前的会话被重定向登录页；1 小时前的会话正常访问（用配置密钥签名构造会话，`TestSessionAbsoluteExpiryForcesRelogin`/`TestSessionWithinExpiryWorks`）。
 
 ## 已确认安全、无需改动
 
@@ -177,4 +184,8 @@
 1. ~~#1（P0）~~ 已完成 2026-08-19
 2. ~~#2、#3、#4（P1）~~ 已完成 2026-08-19
 3. ~~#5-#11（P2）~~ 已完成 2026-08-19
-4. 其余 P3 项随版本迭代
+4. ~~#12-#16（P3）~~ 已完成 2026-08-19
+
+**全部安全审计项已修复完成。** 剩余建议（非代码项）：
+- 部署侧：Caddy 加固（可选，应用层已加安全头）、8080 端口保持仅本机可达、GitHub 仓库中 3 个 50MB+ 的 exe 文件建议改用 LFS 或删除
+- 线上验证：部署新版后检查登录/收件箱/管理页、协议认证封禁、邮件远程图片加载（CSP 影响）