diff --git a/src/index.html b/src/index.html
index 00d4a00..98fa29d 100644
--- a/src/index.html
+++ b/src/index.html
@@ -2,6 +2,7 @@
 <html lang="en">
 <head>
     <meta charset="UTF-8">
+    <meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval' https://cdn.jsdelivr.net; style-src 'self' 'unsafe-inline' https://cdnjs.cloudflare.com; img-src 'self' data: blob: file:; font-src 'self' data:; connect-src 'self' https://www.plantuml.com;">
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>MarkdownConverter</title>
     <link rel="stylesheet" href="fonts.css">
