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Default ruleset for Flask, by r2c.

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Rules (18)

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Data from request object is passed to a new server-side request. This could lead to a server-side request forgery (SSRF). To mitigate, ensure that schemes and hosts are validated against an allowlist, do not forward the response to the user, and ensure proper authentication and transport-layer security in the proxied request.

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Flask response reflects unsanitized user input. This could lead to a cross-site scripting vulnerability (https://owasp.org/www-community/attacks/xss/) in which an attacker causes arbitrary code to be executed in the user's browser. To prevent, please sanitize the user input, e.g. by rendering the response in a Jinja2 template (see considerations in https://flask.palletsprojects.com/en/1.0.x/security/).

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Found a Flask cookie without secure, httponly, or samesite correctly set. Flask cookies should be handled securely by setting secure=True, httponly=True, and samesite='Lax' in response.set_cookie(...). If these parameters are not properly set, your cookies are not properly protected and are at risk of being stolen by an attacker. Include the 'secure=True', 'httponly=True', samesite='Lax' arguments or set these to be true in the Flask configuration.

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Data from request is passed to redirect(). This is an open redirect and could be exploited. Consider using 'url_for()' to generate links to known locations. If you must use a URL to unknown pages, consider using 'urlparse()' or similar and checking if the 'netloc' property is the same as your site's host name. See the references for more information.