Language: Python
Label: vulnerable
CWE: CWE-22 \u2014 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

Code:
def element():
    element_url = src_url = request.args.get('url')
    if element_url.startswith('gAAAAA'):
        try:
            cipher_suite = Fernet(g.session_key)
            src_url = cipher_suite.decrypt(element_url.encode()).decode()
        except (InvalidSignature, InvalidToken) as e:
            return render_template(
                'error.html',
                error_message=str(e)), 401

    src_type = request.args.get('type')

    try:
        file_data = g.user_request.send(base_url=src_url).content
        tmp_mem = io.BytesIO()
        tmp_mem.write(file_data)
        tmp_mem.seek(0)

        return send_file(tmp_mem, mimetype=src_type)
    except exceptions.RequestException:
        pass

    empty_gif = base64.b64decode(
        'R0lGODlhAQABAIAAAP///////yH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==')
    return send_file(io.BytesIO(empty_gif), mimetype='image/gif')