Yasser H. Ali, an Egyptian security researcher, has discovered three critical vulnerabilities in PayPal website which could be used to take control of customer accounts.
Yasser explained in his post the three vulnerabilities used to breach into accounts:
1] Reusable CSRF Token :
The CSRF token “that authenticate every single request made by the user” which can be also found in the request body of every request with the parameter name “Auth” get changed with every request made by user for security measures, but after a deep investigation I found out that the CSRF Auth is Reusable for that specific user email address or username, this means If an attacker found any of these CSRF Tokens, He can then make actions in the behave of any logged in user.
2] Bypassing the CSRF Auth System :
an Attacker can obtain the CSRF Auth which can be valid for ALL users, by intercepting the POST request from a page that provide an Auth Token before the Logging-in process, check this page for the magical CSRF Auth “https://www.paypal.com/eg/cgi-bin/webscr?cmd=_send-money”. At this point the attacker Can CSRF “almost” any request on behave of this user.
3] ByPassing the Security Questions Change :
the request of setting up the security questions “which is initiated by the user while signing up” is not password-protected, and it can be reused to reset the security questions up without providing the password, hence, Armed with the CSRF Auth, an attacker can CSRF this process too and change the victim’s Security questions.
At this point, An attacker can conduct a targeted CSRF attack against a PayPal users and take a full control over his account Hence, An attacker can CSRF all the requests including but not limited to:
― Add/Remove/Confirm Email address
― Add fully privileged users to business account
― Change Security questions
― Change Billing/Shipping Address
― Change Payment methods
― Change user settings (Notifications/Mobile settings)…. and more.
Here is the Proof Of Concept Video:
“The vulnerability is patched very fast and PayPal paid me the maximum bounty they give ($ 10,000 USD) ;)” – Yasser Ali
Original Story: Yasser Ali’s Blog >> Hacking PayPal Accounts with one click