Fix XSS vulnerability by sanitizing user input using escapeHtml function in JavaScript.

zeropath-ai[bot] commented 2 months ago

Summary

The Vulnerability Description: User data flows into the host portion of this manually-constructed HTML, creating a potential Cross-Site-Scripting (XSS) vulnerability if the data comes from user-provided input.
This Fix: Includes an HTML sanitization function that escapes special characters in user input to prevent any arbitrary code execution within the HTML.
The Cause of the Issue: The application directly inserts user-provided data into HTML without sanitizing it, creating an XSS vulnerability.
The Patch Implementation: Introduces a utility function called escapeHtml that replaces special characters with their corresponding HTML entities and uses this function to sanitize the displayName before injecting it into the HTML.

Vulnerability Details

Vulnerability Class: Cross Site Scripting (XSS)
Severity: 7.5
Affected File: examples/express-proxied-server/server.js
Vulnerable Lines: 14-15

Code Snippets

diff --git a/examples/express-proxied-server/server.js b/examples/express-proxied-server/server.js
index e570bf21..d28003dd 100644
--- a/examples/express-proxied-server/server.js
+++ b/examples/express-proxied-server/server.js
@@ -3,6 +3,15 @@ const express = require('express');
 const app = express();
 const PORT = process.env.PORT || 3000;

+function escapeHtml(unsafe) {
+  return unsafe
+    .replace(/&/g, "&amp;")
+    .replace(/</g, "&lt;")
+    .replace(/>/g, "&gt;")
+    .replace(/"/g, "&quot;")
+    .replace(/'/g, "&#039;");
+}
+

 app.get('/', (req, res) => {
   const authenticated = !!req.headers['x-stack-authenticated'];
@@ -11,7 +20,7 @@ app.get('/', (req, res) => {
     <div>
       <p>Main page</p>
       <p>Authenticated: ${authenticated ? "Yes" : "No"}</p>
-      ${authenticated ? `<p>Display Name: ${displayName}</p>` : ""}
+      ${authenticated ? `<p>Display Name: ${escapeHtml(displayName)}</p>` : ""}
       ${authenticated ? `<p><a href="/handler/account-settings" style="text-decoration: underline;">Account Settings</a></p>` : ""}
       <p><a href="/protected" style="text-decoration: underline;">Go to protected page</a></p>
       ${!authenticated ? '<p><a href="/handler/sign-in" style="text-decoration: underline;">Sign In</a></p>' : ""}

How to Modify the Patch

You can modify this patch by using one of the two methods outlined below. We recommend using the ZeroPath bot for updating the code. If you encounter any bugs or issues with the patch, please report them here.

Ask `@zeropath-ai`!

To request modifications, please post a comment beginning with @zeropath-ai and specify the changes required.

@zeropath-ai will then implement the requested adjustments and commit them to the specified branch in this pull request. Our bot is capable of managing changes across multiple files and various development-related requests.

Manually Modify the Files

# Checkout ZeroPath created branch:
git checkout zeropath_fix_cross_site_scripting_xss_1726078977081876

# if vscode is installed run (or use your favorite editor / IDE):
code examples/express-proxied-server/server.js

# Add, commit, and push changes:
git add -A
git commit -m "Update generated patch with x, y, and z changes."
git push zeropath_fix_cross_site_scripting_xss_1726078977081876

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