Fix Reflected XSS in /echo Endpoint by Escaping User Input Using Markupsafe.

[zeropath-ai]

Summary

• The Vulnerability Description: The /echo endpoint in the Python application has a reflected cross-site scripting (XSS) vulnerability due to the inclusion of untrusted input in an HTML response without proper sanitization or escaping. This flaw allows attackers to inject malicious HTML or JavaScript, posing risks like account compromise and session hijacking.

• This Fix: The fix mitigates the XSS vulnerability by escaping untrusted input before it is included in the HTML response. This prevents the execution of potentially harmful scripts injected by attackers.

• The Cause of the Issue: The issue arises from the unsanitized insertion of user-provided input into HTML content, allowing for the potential execution of malicious code sent by an attacker through the /echo endpoint.

• The Patch Implementation: The patch involves using the escape function from the markupsafe library to sanitize user input. This ensures that any HTML or JavaScript content is harmlessly rendered as text instead of being executed when displayed on the page.

Vulnerability Details

• Vulnerability Class: Cross Site Scripting (XSS)
• Severity: 5.3
• Affected File: main.py
• Vulnerable Lines: 96-102

Code Snippets

diff --git a/main.py b/main.py
index 0696be2..4dc3ad6 100644
--- a/main.py
+++ b/main.py
@@ -1,4 +1,5 @@
 from flask import Flask, request, jsonify, session
+from markupsafe import escape
 from werkzeug.security import generate_password_hash, check_password_hash
 import os
 import subprocess
@@ -95,11 +96,12 @@ def get_note(note_id):
 
 @app.route('/echo', methods=['GET'])
 def get_echo():
-
     data = request.json
-    echo = data.get('echo')
-
-    return "<h>" + echo + "</h>", 200
+    echo = data.get('echo', '')
+    
+    # Escape the user input to prevent XSS
+    safe_echo = escape(echo)
+    return f"<h>{safe_echo}</h>", 200
 
 @app.route('/login', methods=['POST'])
 def login():

How to Modify the Patch

You can modify this patch by using one of the two methods outlined below. We recommend using the @zeropath-ai 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 created branch:
git checkout zvuln_fix_cross_site_scripting_xss_1737182341509864

# if vscode is installed run (or use your favorite editor / IDE):
code main.py

# Add, commit, and push changes:
git add -A
git commit -m "Update generated patch with x, y, and z changes."
git push zvuln_fix_cross_site_scripting_xss_1737182341509864