Skip to content


Subversion checkout URL

You can clone with
Download ZIP
Adds security functions to Flask applications for preventing some of the basic threats.
Fetching latest commit...
Cannot retrieve the latest commit at this time.


What is Flask-Mitten?

Adds security functions to Flask applications for preventing some of the basic threats.


Flask-Mitten supports Flask applications to prevent following threats.

  • Clickjacking
  • CSRF
  • Information disclosure through banner grabbing
  • JSON hijacking
  • Session fixation

It bundles functions of following Flask extensions.

More details, see the implementation.



Install the extension with the following commands:

pip install Flask-Mitten


Apply the extention to your app:

from flaskext.mitten import Mitten
app = Flask(__name__)
mitten = Mitten(app)

Request headers are overridden to prevent clickjacking and information disclosure.

If you want to set your own banner, you can do it:

mitten.banner = "My Nice Banner!"

Preventing Session Fixation

After login, call a regenerate method of session object:


The session ID is regenerated, and it prevents session fixation.

To discard a session, call a destroy method:


Preventing CSRF

To embed CSRF token, add following line to your template:

<input type="hidden" name="_csrf_token" value="{{ csrf_token() }}" />

A POST request is protected against CSRF automatically.

If you want to exclude a route from CSRF protection, use a csrf_exempt decorator:

@app.route('/public_api/', methods=['POST'])
def public_api():
    return "result", 200

Preventing JSON Hijacking

If you send a JSON response, you could use a json decorator to avoid JSON hijacking or rendering JSON responses by direct browsing:

def json_api():
    return jsonify(result='success')


For more details, see an example app.

Something went wrong with that request. Please try again.