Fix Reflected XSS Vulnerability in /echo Endpoint by Implementing Input Sanitization

[zeropath-ai]

Summary

• The Vulnerability Description: The /echo/<str:echo> endpoint in the application was exposed to reflected Cross-Site Scripting (XSS), allowing attackers to inject and execute arbitrary HTML or JavaScript by manipulating the echo parameter.
• This Fix: Implementation of input sanitization using the escape function from the markupsafe library ensures that user inputs are safely embedded within the HTML response, preventing execution of injected scripts.
• The Cause of the Issue: The application directly inserted user input from the echo parameter into the HTML response without sanitization, making it susceptible to scripting attacks.
• The Patch Implementation: The patch modifies the endpoint by importing the escape function and applying it to sanitize the echo input before including it in the HTML response, thus neutralizing potential XSS threats.

Vulnerability Details

• Vulnerability Class: Cross Site Scripting (XSS)
• Severity: 6.9
• Affected File: main.py
• Vulnerable Lines: 99-99

Code Snippets

diff --git a/main.py b/main.py
index 8f95e98..01d6364 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
@@ -93,10 +94,9 @@ def get_note(note_id):
 
     return jsonify({"error": "Note not found"}), 404
 
-@app.route('/echo/<str:echo>', methods=['GET'])
+@app.route('/echo/<string:echo>', methods=['GET'])
 def get_echo(echo):
-
-    return "<h>" + echo + "</h>", 200
+    return f"<h>{escape(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.

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Manually Modify the Files

# Checkout created branch:
git checkout zvuln_fix_cross_site_scripting_xss_1737182939895028

# 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_1737182939895028

[r0path]

@zeropath-ai add comments describing the fix

[zeropath-ai]

As per your comment, the following code change has been committed:

diff --git a/main.py b/main.py
index 01d6364..0e5311a 100644
--- a/main.py
+++ b/main.py
@@ -96,6 +96,9 @@ def get_note(note_id):
 
 @app.route('/echo/<string:echo>', methods=['GET'])
 def get_echo(echo):
+    # Using escape() to prevent XSS attacks by escaping special HTML characters
+    # Changed from string concatenation to f-string for better readability
+    # The route parameter type was fixed from 'str' to 'string' to match Flask's conventions
     return f"<h>{escape(echo)}</h>", 200
 
 @app.route('/login', methods=['POST'])

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