Reference: https://cureblog.de/2013/07/phishing-google-wallet-and-paypal-by-abusing-whatsapp/ Phishing Google Wallet and Paypal by abusing WhatsApp -=Introduction=- WhatsApp is one of the most common used tools aka ‘Apps’ on Smarphone-Devices with access to wireless networks or a so called Data-’Flatrate’. By using the internet link to communicate, people do not have to pay any extra fees for sending a text-message somewhere, even if the receiver is in another country. WhatsApp is available for almost every architecture on the market. The program exists for Nokia, Blackberry, Android and iOS. It is available here: https://www.whatsapp.com. This post will focus on the version for android. The app is free for one-year in Android devices. After that time the user has to buy a yearly license. The application provides 3 methods of payment: google wallet paypal payment link. They can be selected via Menu->Settings->Account->Payment Info. -=Bug=- Google-wallet and Paypal payments work in the same way. When selecting it, WhatsApp opens an in-app browser and contacts its main server www.whatsapp.com with the request: /payments/google.php?phone=XXXXXXXXXXXX&cksum=&sku=1&lg=en&lc=US or /payments/paypal.php?phone=XXXXXXXXXXXX&cksum=&sku=1&lg=en&lc=US Responding to this request the browser gets redirected to the proper checkout service. The payment link option seems to be currently not working, i.e., nothing happens. -=Attacks=- Even tough the communication with the payment systems is HTTPS secured, the initial contact with the main server www.whatsapp.com is NOT, as we can see in Wireshark logs: GET /payments/google.php?phone=xxxxxxxxxxxxx&cksum=&sku=1&lg=en&lc=US HTTP/1.1 Host: www.whatsapp.com Accept-Encoding: gzip Accept-Language: en-US User-Agent: Mozilla/5.0 (Linux; U; Android 2.3.7) Cookie: __utmmobile=0xxxxxxxxxxxxxxxxxxxx Accept:application/xml,application/xhtml+xml,text/html; q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 Accept-Charset: utf-8, iso-8859-1, utf-16, *;q=0.7 After Whatsapp sent this unencrypted request, it will receive the following answer. HTTP/1.1 200 OK X-Powered-By: PHP/5.4.7 Content-type: text/html Transfer-Encoding: chunked Date: Mon, 10 May 2013 05:34:36 GMT Server: lighttpd/1.4.31 5e4 WhatsApp Messenger payment

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0 This means an attacker could intercept the first request via a suitable man-in-the-middle attack and successfully redirect the user to any Webpage when the user is trying to buy Whatsapp credit. To gain useraccounts the attacker could setup a fake Google-Wallet or Paypal Systems page to harvest user accounts. It might even be possible to gather directly money through this, for instance let the user pay the 0,99 cents via Google Wallet or Paypal to the account of the attacker. Besides an attacker could forward some other content like a webpage with a new apk necessary for using google-wallet or paypal, like the (in)-famous Zitmo Trojan did at visiting a Bankingsite and spending users some extra “Security”-Features. -=Practical abuse of the bug=- As buying the credit only happens one time per year the attack itself is quite uncommon to be practical for a huge misuse as the attacker needs to be in control of the wireless or gsm network to intercept and redirect the traffic. -=Affected Versions=- 2.9.6447 to 2.10.751 (latest as of 2013 July 2)