This affects all versions of package Flask-Security.
When using the `get_post_logout_redirect` and `get_post_login_redirect` functions, it is possible to bypass URL validation and redirect a user to an arbitrary URL by providing multiple back slashes such as `\\\evil.com/path`.
This vulnerability is only exploitable if an alternative WSGI server other than Werkzeug is used, or the default behaviour of Werkzeug is modified using `'autocorrect_location_header=False`.
**Note:** Flask-Security is not maintained anymore.