diff --git a/fastchat/conversation.py b/fastchat/conversation.py
index 4a46103ec..6c44c7fe7 100644
--- a/fastchat/conversation.py
+++ b/fastchat/conversation.py
@@ -8,6 +8,7 @@
 import base64
 import dataclasses
 from enum import auto, IntEnum
+import html
 from io import BytesIO
 import os
 from typing import List, Any, Dict, Union, Tuple
@@ -370,13 +371,18 @@ def to_gradio_chatbot(self):
                     msg, images = msg
                     image = images[0]  # Only one image on gradio at one time
                     if image.image_format == ImageFormat.URL:
-                        img_str = f'<img src="{image.url}" alt="user upload image" />'
+                        img_str = f'<img src="{html.escape(image.url)}" alt="user upload image" />'
                     elif image.image_format == ImageFormat.BYTES:
-                        img_str = f'<img src="data:image/{image.filetype};base64,{image.base64_str}" alt="user upload image" />'
-                    msg = img_str + msg.replace("<image>\n", "").strip()
+                        img_str = f'<img src="data:image/{html.escape(image.filetype)};base64,{image.base64_str}" alt="user upload image" />'
+                    msg = img_str + html.escape(msg.replace("<image>\n", "").strip())
+                else:
+                    if msg is not None:
+                        msg = html.escape(msg)
 
                 ret.append([msg, None])
             else:
+                if msg is not None:
+                    msg = html.escape(msg)
                 ret[-1][-1] = msg
         return ret
 
diff --git a/fastchat/serve/gradio_block_arena_anony.py b/fastchat/serve/gradio_block_arena_anony.py
index 625c69c44..2c87530b0 100644
--- a/fastchat/serve/gradio_block_arena_anony.py
+++ b/fastchat/serve/gradio_block_arena_anony.py
@@ -480,6 +480,7 @@ def build_side_by_side_ui_anony(models):
                         elem_id="chatbot",
                         height=650,
                         show_copy_button=True,
+                        sanitize_html=True,
                         latex_delimiters=[
                             {"left": "$", "right": "$", "display": False},
                             {"left": "$$", "right": "$$", "display": True},
diff --git a/fastchat/serve/gradio_block_arena_named.py b/fastchat/serve/gradio_block_arena_named.py
index 2f7b39adb..55b5940b5 100644
--- a/fastchat/serve/gradio_block_arena_named.py
+++ b/fastchat/serve/gradio_block_arena_named.py
@@ -358,6 +358,7 @@ def build_side_by_side_ui_named(models):
                         elem_id=f"chatbot",
                         height=650,
                         show_copy_button=True,
+                        sanitize_html=True,
                         latex_delimiters=[
                             {"left": "$", "right": "$", "display": False},
                             {"left": "$$", "right": "$$", "display": True},
diff --git a/fastchat/serve/gradio_block_arena_vision.py b/fastchat/serve/gradio_block_arena_vision.py
index b3d812220..aa05ed6bc 100644
--- a/fastchat/serve/gradio_block_arena_vision.py
+++ b/fastchat/serve/gradio_block_arena_vision.py
@@ -356,6 +356,7 @@ def build_single_vision_language_model_ui(
                 label="Scroll down and start chatting",
                 height=650,
                 show_copy_button=True,
+                sanitize_html=True,
                 latex_delimiters=[
                     {"left": "$", "right": "$", "display": False},
                     {"left": "$$", "right": "$$", "display": True},
diff --git a/fastchat/serve/gradio_block_arena_vision_anony.py b/fastchat/serve/gradio_block_arena_vision_anony.py
index d4d4d484e..c77897d59 100644
--- a/fastchat/serve/gradio_block_arena_vision_anony.py
+++ b/fastchat/serve/gradio_block_arena_vision_anony.py
@@ -432,6 +432,7 @@ def build_side_by_side_vision_ui_anony(context: Context, random_questions=None):
                                 elem_id="chatbot",
                                 height=650,
                                 show_copy_button=True,
+                                sanitize_html=True,
                                 latex_delimiters=[
                                     {"left": "$", "right": "$", "display": False},
                                     {"left": "$$", "right": "$$", "display": True},
diff --git a/fastchat/serve/gradio_block_arena_vision_named.py b/fastchat/serve/gradio_block_arena_vision_named.py
index 7c653acf3..49f48708b 100644
--- a/fastchat/serve/gradio_block_arena_vision_named.py
+++ b/fastchat/serve/gradio_block_arena_vision_named.py
@@ -372,6 +372,7 @@ def build_side_by_side_vision_ui_named(context: Context, random_questions=None):
                                 elem_id=f"chatbot",
                                 height=650,
                                 show_copy_button=True,
+                                sanitize_html=True,
                                 latex_delimiters=[
                                     {"left": "$", "right": "$", "display": False},
                                     {"left": "$$", "right": "$$", "display": True},
diff --git a/fastchat/serve/gradio_web_server.py b/fastchat/serve/gradio_web_server.py
index 8941c6ecb..061a75a93 100644
--- a/fastchat/serve/gradio_web_server.py
+++ b/fastchat/serve/gradio_web_server.py
@@ -927,6 +927,7 @@ def build_single_model_ui(models, add_promotion_links=False):
             label="Scroll down and start chatting",
             height=650,
             show_copy_button=True,
+            sanitize_html=True,
             latex_delimiters=[
                 {"left": "$", "right": "$", "display": False},
                 {"left": "$$", "right": "$$", "display": True},