diff --git a/qlib/contrib/online/manager.py b/qlib/contrib/online/manager.py
index 7475bb6fc52..7107dac570c 100644
--- a/qlib/contrib/online/manager.py
+++ b/qlib/contrib/online/manager.py
@@ -7,6 +7,7 @@
 import pathlib
 import pandas as pd
 import shutil
+import os
 from ruamel.yaml import YAML
 from ...backtest.account import Account
 from .user import User
@@ -43,6 +44,55 @@ def __init__(self, user_data_path, save_report=True):
         self.users = {}
         self.user_record = None
 
+    @staticmethod
+    def _validate_user_id(user_id):
+        """
+        Validate user_id to prevent path traversal / absolute paths.
+
+        user_id is used as a directory name under self.data_path and must not
+        contain path separators, parent traversal, or drive/UNC prefixes.
+        """
+        if not isinstance(user_id, str):
+            raise TypeError("user_id must be a string")
+        if user_id == "" or "\x00" in user_id:
+            raise ValueError("Invalid user_id")
+
+        # Forbid any multi-part paths (e.g. "../x", "a/b", "C:\\x", "\\\\server\\share").
+        parts = pathlib.PurePath(user_id).parts
+        if len(parts) != 1 or parts[0] in (".", ".."):
+            raise ValueError("Invalid user_id")
+
+        # Extra guard: explicit separators (platform-specific and cross-platform)
+        if "/" in user_id or "\\" in user_id:
+            raise ValueError("Invalid user_id")
+
+        return user_id
+
+    def _user_path(self, user_id):
+        """
+        Return the resolved user directory path under self.data_path.
+
+        Ensures the resulting path is contained within self.data_path even if
+        symlinks are involved.
+        """
+        user_id = self._validate_user_id(user_id)
+        base = self.data_path.resolve(strict=False)
+        candidate = (self.data_path / user_id).resolve(strict=False)
+
+        # Ensure candidate is inside base (and on same drive on Windows).
+        try:
+            common = os.path.commonpath([str(base), str(candidate)])
+        except ValueError:
+            # Different drives or invalid paths
+            raise ValueError("Invalid user_id") from None
+
+        if common != str(base):
+            raise ValueError("Invalid user_id")
+        if candidate == base:
+            raise ValueError("Invalid user_id")
+
+        return candidate
+
     def load_users(self):
         """
         load all users' data into manager
@@ -60,9 +110,10 @@ def load_user(self, user_id):
             :return
                 user : User()
         """
-        account_path = self.data_path / user_id
-        strategy_file = self.data_path / user_id / "strategy_{}.pickle".format(user_id)
-        model_file = self.data_path / user_id / "model_{}.pickle".format(user_id)
+        user_path = self._user_path(user_id)
+        account_path = user_path
+        strategy_file = user_path / "strategy_{}.pickle".format(user_id)
+        model_file = user_path / "model_{}.pickle".format(user_id)
         cur_user_list = list(self.users)
         if user_id in cur_user_list:
             raise ValueError("User {} has been loaded".format(user_id))
@@ -82,14 +133,15 @@ def save_user_data(self, user_id):
         """
         if not user_id in self.users:
             raise ValueError("Cannot find user {}".format(user_id))
-        self.users[user_id].account.save_account(self.data_path / user_id)
+        user_path = self._user_path(user_id)
+        self.users[user_id].account.save_account(user_path)
         save_instance(
             self.users[user_id].strategy,
-            self.data_path / user_id / "strategy_{}.pickle".format(user_id),
+            user_path / "strategy_{}.pickle".format(user_id),
         )
         save_instance(
             self.users[user_id].model,
-            self.data_path / user_id / "model_{}.pickle".format(user_id),
+            user_path / "model_{}.pickle".format(user_id),
         )
 
     def add_user(self, user_id, config_file, add_date):
@@ -105,7 +157,7 @@ def add_user(self, user_id, config_file, add_date):
         config_file = pathlib.Path(config_file)
         if not config_file.exists():
             raise ValueError("Cannot find config file {}".format(config_file))
-        user_path = self.data_path / user_id
+        user_path = self._user_path(user_id)
         if user_path.exists():
             raise ValueError("User data for {} already exists".format(user_id))
 
@@ -125,9 +177,9 @@ def add_user(self, user_id, config_file, add_date):
 
         # save user
         user_path.mkdir()
-        save_instance(model, self.data_path / user_id / "model_{}.pickle".format(user_id))
-        save_instance(strategy, self.data_path / user_id / "strategy_{}.pickle".format(user_id))
-        trade_account.save_account(self.data_path / user_id)
+        save_instance(model, user_path / "model_{}.pickle".format(user_id))
+        save_instance(strategy, user_path / "strategy_{}.pickle".format(user_id))
+        trade_account.save_account(user_path)
         user_record = pd.read_csv(self.users_file, index_col=0)
         user_record.loc[user_id] = [add_date]
         user_record.to_csv(self.users_file)
@@ -139,7 +191,7 @@ def remove_user(self, user_id):
             :param
                 user_id : string
         """
-        user_path = self.data_path / user_id
+        user_path = self._user_path(user_id)
         if not user_path.exists():
             raise ValueError("Cannot find user data {}".format(user_id))
         shutil.rmtree(user_path)