One Click Paypal Account Hack

An Egyptian security researcher, Yasser H. Ali has discovered three critical vulnerabilities in PayPal website including CSRF, Auth token bypass and Resetting the security question, which could be used by cybercriminals in the targeted attacks.
Cross-Site Request Forgery (CSRF or XSRF) is a method of attacking a website in which an attacker need to convince the victim to click on a specially crafted HTML exploit page that will make a request to the vulnerable website on their behalf.

This vulnerability enabled my to completely bypass the CSRF Prevention System implemented by PayPal, The vulnerability is patched very fast and PayPal paid me the maximum bounty they give ;). -Yasser H. Ali

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.
Hmm, it seems interesting but still not exploitable, as there is no way for an attacker to get the “Auth” value from a victim session.

2- Bypassing the CSRF Auth System:
The CSRF Auth verifies every single request of that user, So what If an attacker “not logged in” tries to make a “send money” request then PayPal will ask the attacker to provide his email and password, The attacker will provide the “Victim Email” and ANY password, Then he will capture the request, The request will contain a Valid CSRF Auth token Which is Reusable and Can authorise this specific user requests. Upon Further Investigation, We have found out that 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 “”. At this point the attacker Can CSRF “almost” any request on behave of this user.

The application generates a valid "Auth" token for a logged-out user!
The application generates a valid “Auth” token for a logged-out user!
Through examination of the password change process, I have found that an attacker can NOT Change the victim password without answering the Security Questions set by user, Also the user himself can NOT change the security questions without entering the password!

3- ByPassing the Security Questions Change:
Screen Shot 2014-08-13 at 12.20.52 AM

The initial process of “setting” security questions is not password protected and is reusable
After further investigation, I have noticed that 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:

1- Add/Remove/Confirm Email address
2-Add fully privileged users to business account
3- Change Security questions
4- Change Billing/Shipping Address
5- Change Payment methods
6- Change user settings(Notifications/Mobile settings) ………… and more.
To automate the who process, I have coded a Python interactive server to demonstrate how an attacker can exploit this vulnerability in a real-life scenario attack.

Here is the POC Video:

The owner of will not be liable for any errors or omissions in this information nor for the availability of this information. The owner will not be liable for any losses, injuries, or damages from the display or use of this information.Report any Broken Download linkon Blogmytuts Facebook Page. IF YOU WANT TO BORROW MY CONTENT PLEASE CONTACT US..
Share on Google Plus

About Jaime Lacson

A Freelance Computer Tech with knowledge about computer, router and mobile phones, especially in Upgrade and Downgrade OS, Software and Hardware troubleshooting. follow me at Google+
    Blogger Comment
    Facebook Comment