diff --git a/.env.example b/.env.example
index 72d9698..6c5a5cc 100644
--- a/.env.example
+++ b/.env.example
@@ -15,6 +15,12 @@ FLASK_DEBUG=false
 SESSION_LIFETIME_HOURS=24
 SESSION_COOKIE_SECURE=true  # 生产环境HTTPS必须为true，本地HTTP调试可临时设为false
 HTTPS_ENABLED=true
+# 是否信任 X-Forwarded-* 代理头（默认关闭，建议仅在可信反代后开启）
+TRUST_PROXY_HEADERS=false
+# TRUST_PROXY_HEADERS=true 时生效，按需配置你的反向代理网段
+TRUSTED_PROXY_CIDRS=127.0.0.1/32,::1/128
+# 可选：首次启动时指定默认管理员密码（避免控制台输出明文密码）
+# DEFAULT_ADMIN_PASSWORD=your-strong-admin-password
 
 # ==================== 数据库配置 ====================
 DB_FILE=data/app_data.db
@@ -36,6 +42,7 @@ DB_PRAGMA_OPTIMIZE_INTERVAL_SECONDS=21600
 DB_ANALYZE_INTERVAL_SECONDS=86400
 DB_WAL_CHECKPOINT_INTERVAL_SECONDS=43200
 DB_WAL_CHECKPOINT_MODE=PASSIVE
+SYSTEM_CONFIG_CACHE_TTL_SECONDS=30
 
 # ==================== 并发控制配置 ====================
 MAX_CONCURRENT_GLOBAL=2
diff --git a/.gitignore b/.gitignore
index 25452af..f62f0cf 100644
--- a/.gitignore
+++ b/.gitignore
@@ -146,3 +146,7 @@ Thumbs.db
 # Temporary files
 *.tmp
 *.temp
+
+# Allow committed test cases
+!tests/
+!tests/**/*.py
diff --git a/README.md b/README.md
index 320ddea..8b0360a 100644
--- a/README.md
+++ b/README.md
@@ -790,7 +790,8 @@ docker logs -f knowledge-automation-multiuser
 # 6. 访问系统
 # 浏览器打开: http://your-ip:51232
 # 后台管理: http://your-ip:51232/yuyx
-# 默认管理员账号见容器启动日志（首次运行会生成随机密码）
+# 首次管理员密码会写入 data/default_admin_credentials.txt（权限600）
+# 登录后请立即修改密码并删除该文件
 ```
 
 完成！🎉
diff --git a/app.py b/app.py
index b2c9e35..831b28a 100644
--- a/app.py
+++ b/app.py
@@ -49,12 +49,13 @@ from services.tasks import get_task_scheduler
 
 # 设置时区为中国标准时间（CST, UTC+8）
 os.environ["TZ"] = "Asia/Shanghai"
+_TZSET_ERROR = None
 try:
     import time as _time
 
     _time.tzset()
-except Exception:
-    pass
+except Exception as e:
+    _TZSET_ERROR = e
 
 
 def _sigchld_handler(signum, frame):
@@ -116,6 +117,8 @@ except Exception as socketio_error:
 
 init_logging(log_level=config.LOG_LEVEL, log_file=config.LOG_FILE)
 logger = get_logger("app")
+if _TZSET_ERROR is not None:
+    logger.warning(f"设置时区失败，将继续使用系统默认时区: {_TZSET_ERROR}")
 if _socketio_fallback_reason:
     logger.warning(f"[SocketIO] 初始化失败，已回退 threading 模式: {_socketio_fallback_reason}")
 logger.info(f"[SocketIO] 当前 async_mode: {socketio.async_mode}")
@@ -139,15 +142,15 @@ def _request_uses_https() -> bool:
     try:
         if bool(request.is_secure):
             return True
-    except Exception:
-        pass
+    except Exception as e:
+        logger.debug(f"检查 request.is_secure 失败: {e}")
 
     try:
         forwarded_proto = str(request.headers.get("X-Forwarded-Proto", "") or "").split(",", 1)[0].strip().lower()
         if forwarded_proto == "https":
             return True
-    except Exception:
-        pass
+    except Exception as e:
+        logger.debug(f"检查 X-Forwarded-Proto 失败: {e}")
 
     return False
 
@@ -255,8 +258,8 @@ def _record_request_metric_after_response(response) -> None:
                 logger.warning(
                     f"[API-DIAG] {method} {path} -> {status_code} ({duration_ms:.1f}ms)"
                 )
-    except Exception:
-        pass
+    except Exception as e:
+        logger.debug(f"记录请求指标失败: {e}")
 
 
 @app.after_request
@@ -312,12 +315,12 @@ def serve_static(filename):
     # 协商缓存：确保存在 ETag，并基于 If-None-Match/If-Modified-Since 返回 304
     try:
         response.add_etag(overwrite=False)
-    except Exception:
-        pass
+    except Exception as e:
+        logger.debug(f"静态资源 ETag 设置失败({filename}): {e}")
     try:
         response.make_conditional(request)
-    except Exception:
-        pass
+    except Exception as e:
+        logger.debug(f"静态资源协商缓存处理失败({filename}): {e}")
 
     response.headers.setdefault("Vary", "Accept-Encoding")
     if is_hashed_asset:
@@ -341,33 +344,33 @@ def cleanup_on_exit():
             for acc in accounts.values():
                 if getattr(acc, "is_running", False):
                     acc.should_stop = True
-    except Exception:
-        pass
+    except Exception as e:
+        logger.warning(f"停止运行中任务失败: {e}")
 
     logger.info("- 停止任务调度器...")
     try:
         scheduler = get_task_scheduler()
         scheduler.shutdown(timeout=5)
-    except Exception:
-        pass
+    except Exception as e:
+        logger.warning(f"停止任务调度器失败: {e}")
 
     logger.info("- 关闭截图线程池...")
     try:
         shutdown_browser_worker_pool()
-    except Exception:
-        pass
+    except Exception as e:
+        logger.warning(f"关闭截图线程池失败: {e}")
 
     logger.info("- 关闭邮件队列...")
     try:
         email_service.shutdown_email_queue()
-    except Exception:
-        pass
+    except Exception as e:
+        logger.warning(f"关闭邮件队列失败: {e}")
 
     logger.info("- 关闭数据库连接池...")
     try:
         db_pool._pool.close_all() if db_pool._pool else None
-    except Exception:
-        pass
+    except Exception as e:
+        logger.warning(f"关闭数据库连接池失败: {e}")
 
     logger.info("[OK] 资源清理完成")
 
@@ -464,7 +467,7 @@ def _log_startup_urls() -> None:
     logger.info("服务器启动中...")
     logger.info(f"用户访问地址: http://{config.SERVER_HOST}:{config.SERVER_PORT}")
     logger.info(f"后台管理地址: http://{config.SERVER_HOST}:{config.SERVER_PORT}/yuyx")
-    logger.info("默认管理员: admin (首次运行随机密码见日志)")
+    logger.info("默认管理员: admin (首次运行密码写入 data/default_admin_credentials.txt)")
     logger.info("=" * 60)
 
 
diff --git a/app_security.py b/app_security.py
index 4bce639..7b1b5b9 100755
--- a/app_security.py
+++ b/app_security.py
@@ -197,6 +197,9 @@ class IPRateLimiter:
 # 全局IP限流器实例
 ip_rate_limiter = IPRateLimiter()
 
+_TRUTHY_VALUES = {"1", "true", "yes", "on"}
+_TRUST_PROXY_HEADERS = str(os.environ.get("TRUST_PROXY_HEADERS", "false") or "").strip().lower() in _TRUTHY_VALUES
+
 
 def require_ip_not_locked(f):
     """装饰器：检查IP是否被锁定"""
@@ -443,7 +446,7 @@ def get_client_ip(trust_proxy=False):
     """
     # 安全说明：X-Forwarded-For 可被伪造
     # 仅在确认请求来自可信代理时才使用代理头
-    if trust_proxy:
+    if trust_proxy and _TRUST_PROXY_HEADERS:
         if request.headers.get('X-Forwarded-For'):
             return request.headers.get('X-Forwarded-For').split(',')[0].strip()
         elif request.headers.get('X-Real-IP'):
@@ -455,7 +458,7 @@ def get_client_ip(trust_proxy=False):
 
 def _load_trusted_proxy_networks():
     """加载可信代理 CIDR 列表。"""
-    default_cidrs = "127.0.0.1/32,::1/128,10.0.0.0/8,172.16.0.0/12,192.168.0.0/16,fc00::/7"
+    default_cidrs = "127.0.0.1/32,::1/128"
     raw = str(os.environ.get("TRUSTED_PROXY_CIDRS", default_cidrs) or "").strip()
     if not raw:
         return []
@@ -525,6 +528,9 @@ def _extract_real_ip_from_forwarded_chain() -> str | None:
 def get_rate_limit_ip() -> str:
     """在可信代理场景下取真实IP，用于限流/风控。"""
     remote_addr = request.remote_addr or ""
+    if not _TRUST_PROXY_HEADERS:
+        return remote_addr
+
     remote_ip = _parse_ip_address(remote_addr)
     if remote_ip is None:
         return remote_addr
diff --git a/crypto_utils.py b/crypto_utils.py
index de7986d..b937aad 100644
--- a/crypto_utils.py
+++ b/crypto_utils.py
@@ -119,15 +119,11 @@ def get_encryption_key():
             "2. 或在 docker-compose.yml 中设置 ENCRYPTION_KEY_RAW 环境变量\n"
             "3. 如果密钥确实丢失，需要重新录入所有账号密码\n"
             "\n"
-            "设置 ALLOW_NEW_KEY=true 环境变量可强制生成新密钥（不推荐）\n"
             + "=" * 60
         )
         logger.error(error_msg)
-        
-        # 检查是否强制允许生成新密钥
-        if os.environ.get('ALLOW_NEW_KEY', '').lower() != 'true':
-            print(error_msg, file=sys.stderr)
-            raise RuntimeError("加密密钥丢失且存在已加密数据，请检查配置")
+        print(error_msg, file=sys.stderr)
+        raise RuntimeError("加密密钥丢失且存在已加密数据，请恢复密钥后再启动")
 
     # 生成新的密钥
     key = Fernet.generate_key()
diff --git a/database.py b/database.py
index c4fb0d4..64a3406 100644
--- a/database.py
+++ b/database.py
@@ -19,6 +19,7 @@ from typing import Optional
 
 import db_pool
 from app_config import get_config
+from app_logger import get_logger
 
 from db.schema import ensure_schema
 from db.migrations import migrate_database as _migrate_database
@@ -126,6 +127,7 @@ from db.users import (
 from db.security import record_login_context
 
 config = get_config()
+logger = get_logger(__name__)
 
 # 数据库文件路径
 DB_FILE = config.DB_FILE
@@ -140,9 +142,9 @@ _system_config_cache_lock = threading.Lock()
 _system_config_cache_value: Optional[dict] = None
 _system_config_cache_loaded_at = 0.0
 try:
-    _SYSTEM_CONFIG_CACHE_TTL_SECONDS = float(os.environ.get("SYSTEM_CONFIG_CACHE_TTL_SECONDS", "3"))
+    _SYSTEM_CONFIG_CACHE_TTL_SECONDS = float(os.environ.get("SYSTEM_CONFIG_CACHE_TTL_SECONDS", "30"))
 except Exception:
-    _SYSTEM_CONFIG_CACHE_TTL_SECONDS = 3.0
+    _SYSTEM_CONFIG_CACHE_TTL_SECONDS = 30.0
 _SYSTEM_CONFIG_CACHE_TTL_SECONDS = max(0.0, _SYSTEM_CONFIG_CACHE_TTL_SECONDS)
 
 
@@ -197,8 +199,8 @@ def init_database():
     try:
         config_value = get_system_config()
         db_pool.configure_slow_query_runtime(threshold_ms=config_value.get("db_slow_query_ms"))
-    except Exception:
-        pass
+    except Exception as e:
+        logger.warning(f"初始化慢查询阈值失败，使用默认值: {e}")
 
 
 def migrate_database():
@@ -293,6 +295,6 @@ def update_system_config(
         try:
             latest_config = get_system_config()
             db_pool.configure_slow_query_runtime(threshold_ms=latest_config.get("db_slow_query_ms"))
-        except Exception:
-            pass
+        except Exception as e:
+            logger.warning(f"更新慢查询阈值失败，保留当前配置: {e}")
     return ok
diff --git a/db/admin.py b/db/admin.py
index 088220f..b9b5255 100644
--- a/db/admin.py
+++ b/db/admin.py
@@ -2,7 +2,9 @@
 # -*- coding: utf-8 -*-
 from __future__ import annotations
 
+import os
 import sqlite3
+from pathlib import Path
 
 import db_pool
 from db.utils import get_cst_now_str
@@ -109,6 +111,28 @@ def _normalize_days(days, default: int = 30) -> int:
     return value
 
 
+def _store_default_admin_credentials(username: str, password: str) -> str | None:
+    """将首次管理员账号密码写入受限权限文件，避免打印到日志。"""
+    raw_path = str(
+        os.environ.get("DEFAULT_ADMIN_CREDENTIALS_FILE", "data/default_admin_credentials.txt") or ""
+    ).strip()
+    if not raw_path:
+        return None
+
+    cred_path = Path(raw_path)
+    try:
+        cred_path.parent.mkdir(parents=True, exist_ok=True)
+        with open(cred_path, "w", encoding="utf-8") as f:
+            f.write("安全提醒：首次管理员账号已创建\n")
+            f.write(f"用户名: {username}\n")
+            f.write(f"密码: {password}\n")
+            f.write("请登录后立即修改密码，并删除该文件。\n")
+        os.chmod(cred_path, 0o600)
+        return str(cred_path)
+    except Exception:
+        return None
+
+
 def ensure_default_admin() -> bool:
     """确保存在默认管理员账号（行为保持不变）。"""
     import secrets
@@ -120,7 +144,8 @@ def ensure_default_admin() -> bool:
 
         if count == 0:
             alphabet = string.ascii_letters + string.digits
-            random_password = "".join(secrets.choice(alphabet) for _ in range(12))
+            bootstrap_password = str(os.environ.get("DEFAULT_ADMIN_PASSWORD", "") or "").strip()
+            random_password = bootstrap_password or "".join(secrets.choice(alphabet) for _ in range(12))
 
             default_password_hash = hash_password_bcrypt(random_password)
             cursor.execute(
@@ -128,11 +153,16 @@ def ensure_default_admin() -> bool:
                 ("admin", default_password_hash, get_cst_now_str()),
             )
             conn.commit()
+            credential_file = _store_default_admin_credentials("admin", random_password)
             print("=" * 60)
             print("安全提醒：已创建默认管理员账号")
             print("用户名: admin")
-            print(f"密码: {random_password}")
-            print("请立即登录后修改密码！")
+            if credential_file:
+                print(f"初始密码已写入: {credential_file}（权限600）")
+                print("请立即登录后修改密码，并删除该文件。")
+            else:
+                print("未能写入初始密码文件。")
+                print("建议设置 DEFAULT_ADMIN_PASSWORD 后重建管理员账号。")
             print("=" * 60)
             return True
         return False
diff --git a/db/users.py b/db/users.py
index c5cf5d1..81b343f 100644
--- a/db/users.py
+++ b/db/users.py
@@ -21,6 +21,10 @@ logger = get_logger(__name__)
 
 _CST_TZ = pytz.timezone("Asia/Shanghai")
 _PERMANENT_VIP_EXPIRE = "2099-12-31 23:59:59"
+_USER_LOOKUP_SQL = {
+    "id": "SELECT * FROM users WHERE id = ?",
+    "username": "SELECT * FROM users WHERE username = ?",
+}
 
 
 def _row_to_dict(row):
@@ -28,9 +32,12 @@ def _row_to_dict(row):
 
 
 def _get_user_by_field(field_name: str, field_value):
+    query_sql = _USER_LOOKUP_SQL.get(str(field_name or ""))
+    if not query_sql:
+        raise ValueError(f"unsupported user lookup field: {field_name}")
     with db_pool.get_db() as conn:
         cursor = conn.cursor()
-        cursor.execute(f"SELECT * FROM users WHERE {field_name} = ?", (field_value,))
+        cursor.execute(query_sql, (field_value,))
         return _row_to_dict(cursor.fetchone())
 
 
diff --git a/routes/api_auth.py b/routes/api_auth.py
index aba8c68..26514d2 100644
--- a/routes/api_auth.py
+++ b/routes/api_auth.py
@@ -201,8 +201,8 @@ def _send_login_security_alert_if_needed(user: dict, username: str, client_ip: s
             new_device=context.get("new_device", False),
             user_id=user["id"],
         )
-    except Exception:
-        pass
+    except Exception as e:
+        logger.warning(f"发送登录安全提醒失败: user_id={user.get('id')}, error={e}")
 
 
 def _parse_credential_payload(data: dict) -> dict | None:
@@ -308,10 +308,9 @@ def verify_email(token):
     if result:
         token_id = result["token_id"]
         user_id = result["user_id"]
-        email = result["email"]
 
         if not database.approve_user(user_id):
-            logger.error(f"用户邮箱验证失败: 用户审核更新失败 user_id={user_id}, email={email}")
+            logger.error(f"用户邮箱验证失败: 用户审核更新失败 user_id={user_id}")
             error_message = "验证处理失败，请稍后重试"
             spa_initial_state = {
                 "page": "verify_result",
@@ -333,9 +332,9 @@ def verify_email(token):
             database.set_user_vip(user_id, auto_approve_vip_days)
 
         if not email_service.consume_email_token(token_id):
-            logger.warning(f"用户邮箱验证后Token消费失败: token_id={token_id}, user_id={user_id}")
+            logger.warning(f"用户邮箱验证后Token消费失败: user_id={user_id}")
 
-        logger.info(f"用户邮箱验证成功: user_id={user_id}, email={email}")
+        logger.info(f"用户邮箱验证成功: user_id={user_id}")
         spa_initial_state = {
             "page": "verify_result",
             "success": True,
@@ -348,7 +347,7 @@ def verify_email(token):
         }
         return render_app_spa_or_legacy("verify_success.html", spa_initial_state=spa_initial_state)
 
-    logger.warning(f"邮箱验证失败: token={token[:20]}...")
+    logger.warning("邮箱验证失败: token无效或已过期")
     error_message = "验证链接无效或已过期，请重新注册或申请重发验证邮件"
     spa_initial_state = {
         "page": "verify_result",
diff --git a/routes/api_user.py b/routes/api_user.py
index ea79c0c..800bd74 100644
--- a/routes/api_user.py
+++ b/routes/api_user.py
@@ -365,7 +365,7 @@ def verify_bind_email(token):
 
         if database.update_user_email(user_id, email, verified=True):
             if not email_service.consume_email_token(token_id):
-                logger.warning(f"邮箱绑定成功但Token消费失败: token_id={token_id}, user_id={user_id}")
+                logger.warning(f"邮箱绑定成功但Token消费失败: user_id={user_id}")
             return _render_verify_bind_success(email)
 
         return _render_verify_bind_failed(title="绑定失败", error_message="邮箱绑定失败，请重试")
diff --git a/tests/test_security_hardening.py b/tests/test_security_hardening.py
new file mode 100644
index 0000000..bf32e09
--- /dev/null
+++ b/tests/test_security_hardening.py
@@ -0,0 +1,58 @@
+import importlib
+import sys
+from pathlib import Path
+
+import pytest
+from flask import Flask
+
+PROJECT_ROOT = Path(__file__).resolve().parents[1]
+if str(PROJECT_ROOT) not in sys.path:
+    sys.path.insert(0, str(PROJECT_ROOT))
+
+import app_security
+import crypto_utils
+from db import users as db_users
+
+
+def test_user_lookup_rejects_dynamic_field_name():
+    with pytest.raises(ValueError):
+        db_users._get_user_by_field("username OR 1=1 --", "demo")
+
+
+def test_rate_limit_ip_does_not_trust_proxy_headers_by_default(monkeypatch):
+    monkeypatch.delenv("TRUST_PROXY_HEADERS", raising=False)
+    monkeypatch.delenv("TRUSTED_PROXY_CIDRS", raising=False)
+    security_module = importlib.reload(app_security)
+
+    app = Flask(__name__)
+    with app.test_request_context(
+        "/",
+        environ_base={"REMOTE_ADDR": "10.0.0.9"},
+        headers={"X-Forwarded-For": "198.51.100.10"},
+    ):
+        assert security_module.get_rate_limit_ip() == "10.0.0.9"
+
+
+def test_rate_limit_ip_can_use_forwarded_chain_when_explicitly_enabled(monkeypatch):
+    monkeypatch.setenv("TRUST_PROXY_HEADERS", "true")
+    monkeypatch.setenv("TRUSTED_PROXY_CIDRS", "10.0.0.0/8")
+    security_module = importlib.reload(app_security)
+
+    app = Flask(__name__)
+    with app.test_request_context(
+        "/",
+        environ_base={"REMOTE_ADDR": "10.2.3.4"},
+        headers={"X-Forwarded-For": "198.51.100.10, 10.2.3.4"},
+    ):
+        assert security_module.get_rate_limit_ip() == "198.51.100.10"
+
+
+def test_get_encryption_key_refuses_regeneration_when_encrypted_data_exists(monkeypatch, tmp_path):
+    monkeypatch.setenv("ALLOW_NEW_KEY", "true")
+    monkeypatch.delenv("ENCRYPTION_KEY_RAW", raising=False)
+    monkeypatch.delenv("ENCRYPTION_KEY", raising=False)
+    monkeypatch.setattr(crypto_utils, "ENCRYPTION_KEY_FILE", str(tmp_path / "missing_key.bin"))
+    monkeypatch.setattr(crypto_utils, "_check_existing_encrypted_data", lambda: True)
+
+    with pytest.raises(RuntimeError):
+        crypto_utils.get_encryption_key()