diff --git a/dargs/notebook.py b/dargs/notebook.py
index c705dbf..61d851c 100644
--- a/dargs/notebook.py
+++ b/dargs/notebook.py
@@ -259,11 +259,11 @@ def print_html(self, _level: int = 0, _last_one: bool = True) -> str:
             buff.append(r"""<code class="dargs-code">""")
             buff.append('"')
             if isinstance(self.arg, Argument):
-                buff.append(self.arg.name)
+                buff.append(html.escape(self.arg.name, quote=False))
             elif isinstance(self.arg, Variant):
-                buff.append(self.arg.flag_name)
+                buff.append(html.escape(self.arg.flag_name, quote=False))
             elif isinstance(self.arg, str):
-                buff.append(self.arg)
+                buff.append(html.escape(self.arg, quote=False))
             else:
                 raise ValueError(f"Unknown type: {type(self.arg)}")
             buff.append('"')
@@ -276,6 +276,9 @@ def print_html(self, _level: int = 0, _last_one: bool = True) -> str:
                         .replace("| type:", "type:")
                         .replace("\n", linebreak)
                     )
+                    # Escape generated text before selectively restoring the small
+                    # set of formatting markers supported by the tooltip.
+                    doc_head = html.escape(doc_head, quote=False)
                     # use re to replace ``xx`` to <code>xx</code>
                     doc_head = re.sub(
                         r"``(.*?)``",
@@ -285,19 +288,21 @@ def print_html(self, _level: int = 0, _last_one: bool = True) -> str:
                     doc_head = re.sub(r"\*(.+)\*", r"<i>\1</i>", doc_head)
                     buff.append(doc_head)
                 elif isinstance(self.arg, Variant):
-                    buff.append(f"{self.arg.flag_name}:<br/>type: ")
+                    buff.append(
+                        f"{html.escape(self.arg.flag_name, quote=False)}:<br/>type: "
+                    )
                     buff.append(r"""<span class="dargs-doc-code">""")
                     buff.append("str")
                     buff.append(r"""</span>""")
                     if self.arg.default_tag:
                         buff.append(", default: ")
                         buff.append(r"""<span class="dargs-doc-code">""")
-                        buff.append(self.arg.default_tag)
+                        buff.append(html.escape(self.arg.default_tag, quote=False))
                         buff.append(r"""</span>""")
                 else:
                     raise ValueError(f"Unknown type: {type(self.arg)}")
 
-                doc_body = html.escape(self.arg.doc.strip())
+                doc_body = html.escape(self.arg.doc.strip(), quote=False)
                 if doc_body:
                     buff.append("<hr/>")
                 doc_body = re.sub(r"""\n+""", "\n", doc_body)
@@ -348,7 +353,7 @@ def print_html(self, _level: int = 0, _last_one: bool = True) -> str:
         else:
             buff.append(r"""<code class="dargs-code">""")
             buff.append(
-                json.dumps(self.data, indent=2)
+                html.escape(json.dumps(self.data, indent=2), quote=False)
                 .replace(" ", "&nbsp;")
                 .replace(
                     "\n", f"""</code>{linebreak}{indent}<code class="dargs-code">"""
diff --git a/tests/test_notebook.py b/tests/test_notebook.py
index 6184197..2113665 100644
--- a/tests/test_notebook.py
+++ b/tests/test_notebook.py
@@ -15,6 +15,26 @@
 
 @unittest.skipUnless(ipython_installed, "IPython not installed")
 class TestNotebook(unittest.TestCase):
+    def test_html_escapes_user_content(self) -> None:
+        """JSON values, keys, and docs cannot inject executable HTML."""
+        from dargs.notebook import print_html
+
+        dangerous_key = '<img src="x" onerror="alert(1)">'
+        argument = Argument(
+            "root",
+            dict,
+            [Argument(dangerous_key, str, doc="<script>doc()</script>")],
+        )
+        rendered = print_html(
+            {dangerous_key: "<script>value()</script>"},
+            argument,
+        )
+
+        self.assertNotIn("<script>", rendered)
+        self.assertNotIn("<img ", rendered)
+        self.assertIn("&lt;script&gt;value()", rendered)
+        self.assertIn("&lt;img src=", rendered)
+
     def test_html_validation(self) -> None:
         from dargs.notebook import print_html