Flask Development Python Web Design

How to prevent Cross-Site Request Forgery (CSRF) attacks in flask App


Cross-Site Request Forgery (CSRF) is an attack that forces authenticated users to submit a request to a Web application against which they are currently authenticated. CSRF attacks exploit the trust a Web application has in an authenticated user.

To prevent Cross-Site Request Forgery (CSRF) attacks in your Flask application, you can use Flask’s built-in CSRF protection mechanism called “Flask-WTF” (Flask Web Forms). Flask-WTF provides a simple way to protect your forms against CSRF attacks. Here’s how you can solve the CSRF issue:

  1. Install Flask-WTF: If you haven’t already, you need to install Flask-WTF. You can do this using pip:
   pip install Flask-WTF
  1. Import and Configure Flask-WTF: In your Flask application, import and configure Flask-WTF. Typically, you would create a Flask-WTF extension object and initialize it with your app:
   from flask import Flask
   from flask_wtf.csrf import CSRFProtect

   app = Flask(__name__)
   csrf = CSRFProtect(app)
  1. Use Flask-WTF for Form Handling: When you create forms in your application, use Flask-WTF’s csrf_token field in your forms. For example, using Flask-WTF’s FlaskForm class:
   from flask_wtf import FlaskForm
   from wtforms import StringField, SubmitField

   class MyForm(FlaskForm):
       name = StringField('Name')
       submit = SubmitField('Submit')
  1. Include CSRF Token in Your HTML Forms: In your HTML templates, include the CSRF token using the csrf_token field in your form:
   <form method="POST">
       {{ form.csrf_token }}
       {{ form.hidden_tag() }}
       <!-- Other form fields here -->
       <button type="submit">Submit</button>
  1. Ensure CSRF Protection in All Routes: Flask-WTF automatically checks and validates the CSRF token in incoming POST requests. Make sure that you’re using @app.route decorators for your routes and that you’re using the methods argument with ‘POST’ for routes that modify data.
   @app.route('/some_route', methods=['GET', 'POST'])
   def some_route():
       form = MyForm()
       if form.validate_on_submit():
           # Handle the form submission
       return render_template('some_template.html', form=form)
  1. Testing: After implementing Flask-WTF and including CSRF protection in your forms, test your application to ensure that CSRF attacks are effectively prevented.

With Flask-WTF’s CSRF protection in place, your application should be more secure against CSRF attacks, as it will generate and verify unique CSRF tokens for each user session, making it much harder for malicious attackers to forge requests.

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