Flask uses cookie based sessions by default, but there is support for custom sessions that store data in other places. … When the session data is stored in the server you can be sure that any data that you write to it is as secure as your server .
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Flask – Sessions A session with each client is assigned a Session ID . The Session data is stored on top of cookies and the server signs them cryptographically. For this encryption, a Flask application needs a defined SECRET_KEY.
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