Document Title: =============== PayPal Bug Bounty #119 - Stored Cross Site Scripting Vulnerability References (Source): ==================== http://www.vulnerability-lab.com/get_content.php?id=1588 Video: http://www.vulnerability-lab.com/get_content.php?id=1587 Vulnerability Magazine: http://magazine.vulnerability-db.com/?q=articles/2015/08/28/paypal-inc-bug-bounty-2015-stored-cross-site-vulnerability-disclosed-researcher Release Date: ============= 2015-08-28 Vulnerability Laboratory ID (VL-ID): ==================================== 1588 Common Vulnerability Scoring System: ==================================== 4.2 Product & Service Introduction: =============================== PayPal is a global e-commerce business allowing payments and money transfers to be made through the Internet. Online money transfers serve as electronic alternatives to paying with traditional paper methods, such as checks and money orders. Originally, a PayPal account could be funded with an electronic debit from a bank account or by a credit card at the payer s choice. But some time in 2010 or early 2011, PayPal began to require a verified bank account after the account holder exceeded a predetermined spending limit. After that point, PayPal will attempt to take funds for a purchase from funding sources according to a specified funding hierarchy. If you set one of the funding sources as Primary, it will default to that, within that level of the hierarchy (for example, if your credit card ending in 4567 is set as the Primary over 1234, it will still attempt to pay money out of your PayPal balance, before it attempts to charge your credit card). The funding hierarchy is a balance in the PayPal account; a PayPal credit account, PayPal Extras, PayPal SmartConnect, PayPal Extras Master Card or Bill Me Later (if selected as primary funding source) (It can bypass the Balance); a verified bank account; other funding sources, such as non-PayPal credit cards. The recipient of a PayPal transfer can either request a check from PayPal, establish their own PayPal deposit account or request a transfer to their bank account. PayPal is an acquirer, performing payment processing for online vendors, auction sites, and other commercial users, for which it charges a fee. It may also charge a fee for receiving money, proportional to the amount received. The fees depend on the currency used, the payment option used, the country of the sender, the country of the recipient, the amount sent and the recipient s account type. In addition, eBay purchases made by credit card through PayPal may incur extra fees if the buyer and seller use different currencies. On October 3, 2002, PayPal became a wholly owned subsidiary of eBay. Its corporate headquarters are in San Jose, California, United States at eBay s North First Street satellite office campus. The company also has significant operations in Omaha, Nebraska, Scottsdale, Arizona, and Austin, Texas, in the United States, Chennai, Dublin, Kleinmachnow (near Berlin) and Tel Aviv. As of July 2007, across Europe, PayPal also operates as a Luxembourg-based bank. On March 17, 2010, PayPal entered into an agreement with China UnionPay (CUP), China s bankcard association, to allow Chinese consumers to use PayPal to shop online.PayPal is planning to expand its workforce in Asia to 2,000 by the end of the year 2010. (Copy of the Homepage: www.paypal.com) [http://en.wikipedia.org/wiki/PayPal] Abstract Advisory Information: ============================== The Vulnerability Laboratory Core Team Researcher discovered an application-side input validation and filter bypass vulnerability in the official PayPal Inc online service web-application. Vulnerability Disclosure Timeline: ================================== 2015-08-20: Vendor Fix/Patch (PayPal Inc - Developer Team) 2015-08-28: Public Disclosure (Vulnerability Laboratory Discovery Status: ================= Published Affected Product(s): ==================== PayPal Inc Product: PayPal - Online Service Web Application 2015 Q3 Exploitation Technique: ======================= Remote Severity Level: =============== Medium Technical Details & Description: ================================ An application-side validation vulnerability has been discovered in the official PayPal Inc online service web-application. The vulnerability allows remote attackers to comrpomise user accounts or transactions by persistent malicious inject of script codes. Paypal SecurePayments domain is used by paypal users to do secure payments when purchasing from any shopping site, this secure payments page require Paypal users to fill some forms that include their Credit Card number, CVV2, Expiry date and more to finalize the payment and purchase the products via their Paypal account, The submitted data is processed through encrypted channel(HTTPS) so attackers wont be able to sniff/steal such data. I’ve found a Stored XSS vulnerability that affects the SecurePayment page directly which allowed me to alter the page HTML and rewrite the page content, An attacker can provide his own HTML forms to the user to fullfill and send the users data back to attacker’s server in clear text format, and then use this information to purchase anything in behave of users or even transfere the users fund to his own account! Request Method(s): [+] POST Vulnerable Page: [+] https://securepayments.paypal.com/cgi-bin/acquiringweb Vulnerable Parameter(s): [+] template Proof of Concept (PoC): ======================= The application-side cross site scripting vulnerability can be exploited by remote attackers withour privilege application user account and with low user interaction (click). For security demonstration or to reproduce the vulnerability follow the provided information and steps below to continue. Manual steps to reproduce the vulnerability ... 1- Attacker setup shopping site or Hack into any shopping site, alter the “CheckOut” button with the Paypal Vulnerability, 2- Paypal user browse the malformed shopping site, choose some products, click on “CheckOut” button to Pay with his Paypal account, 3- User get’s redirected to https://Securepayments.Paypal.com/ to fill the required Credit Card information to complete the purchasing order, In the same page, the products price that will be paid is included inside the same page, and as we know the attacker now control this page! 4- Now when you (Paypal user) click on Submit Payment button, instead of paying let’s say “100$” YOU WILL PAY TO THE ATTACKER WHATEVER AMOUNT THE ATTACKER’S DECIDE!! Solution - Fix & Patch: ======================= 2015-08-20: Vendor Fix/Patch (PayPal Inc - Developer Team) Security Risk: ============== The security risk of the stored cross site scripting vulnerability in the paypal web-application is estimated as medium. (CVSS 4.2) Credits & Authors: ================== Vulnerability Laboratory [Research Team] - Ebrahim Hegazy [ebrahim@evolution-sec.com] (www.vulnerability-lab.com) Disclaimer & Information: ========================= The information provided in this advisory is provided as it is without any warranty. Vulnerability Lab disclaims all warranties, either expressed or implied, including the warranties of merchantability and capability for a particular purpose. Vulnerability-Lab or its suppliers are not liable in any case of damage, including direct, indirect, incidental, consequential loss of business profits or special damages, even if Vulnerability-Lab or its suppliers have been advised of the possibility of such damages. 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