Document Title: =============== PayPal Inc #168 - Insufficient Authentication Vulnerability Date: ===== 2017-10-30 References: =========== https://www.vulnerability-lab.com/get_content.php?id=2091 VL-ID: ===== 2091 Common Vulnerability Scoring System: ==================================== 4.2 Vulnerability Class: ==================== Enumeration 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. (Copy of the Homepage: www.paypal.com) [http://en.wikipedia.org/wiki/PayPal] Abstract: ========= The vulnerability laboratory research team discovered multiple vulnerabilities in the official PayPal Inc Marketing online service web-application. Report-Timeline: ================ 2017-08-28: Researcher Notification & Coordination (Core Security Researcher) 2017-08-29: Vendor Notification (PayPal Inc Security Department) 2017-09-05: Vendor Response/Feedback (PayPal Inc Security Department) 2017-10-20: Vendor Fix/Patch (PayPal Inc Service Developer Team) 2017-10-29: Security Acknowledgements (PayPal Inc Security Department) 2017-10-30: Public Disclosure (Vulnerability Laboratory) Status: ======== Published Affected Products: ================== Exploitation-Technique: ======================= Remote Severity: ========= Medium Details: ======== An insufficient authentication issue has been discovered in the official PayPal Inc Marketing online service web-application. The vulnerability can be used by remote attackers to enumerate email addresses of the paypal users in the web-application. The issue allows as well to get more details about teams associated with that email addresses. The request method to exploit is GET and the attack vector is located on the client-side of the paypal marketing online service web-application. The issue is located in the authentication process of the gift method via the send money by email. The security risk of the vulnerability is estimated as medium with a cvss (common vulnerability scoring system) count of 4.2. Exploitation of the insufficient authentication web vulnerability requires a low privileged web-application user account and no user interaction. Successful exploitation of the vulnerability results disclosure of sensitive information. Request Method(s): [+] POST Vulnerable Module(s): [+] signup business account Affected Module(s): [+] email verification redirect Proof of Concept: ================= The security issue can be exploited by remote attackers without privileged user account and without user interaction. For security demonstration or to reproduce the vulnerability follow the provided information and steps below to continue. Location: The bug is located in the sign up business account which uses the email to check Example: (URL - Request) https://www.paypal.com/bizsignup/flows/americas/standard/check-account-existence email[value]:email.attacker@gmail.com email[isValidated]:true pageName:checkAccount pageCompletions[checkAccount]:false pageCompletions[createPassword]:false pageCompletions[create]:false pageCompletions[businessInfo]:false pageCompletions[personalInfo]:false pageCompletions[upgradeBusinessAccount]:false Redirect : https://www.paypal.com/bizsignup/#/createPassword << means account not exist Redirect : https://www.paypal.com/signin?country.x=US&locale.x=en_US << account exist Note: A simple redirect check can be used to enumerate user account emails of paypal Solution: ========= The vulnerability can be patched by approval of the authentication in the marketing application to add some brute force protection (example: captcha). Risk: ===== The security risk of the insufficient authentication vulnerability in the paypal market web-application is estimated as medium. (CVSS 4.2) Credits: ======== Vulnerability Laboratory [Research Team] Chamli [mohamed.chamli@esprit.tn] - https://www.vulnerability-lab.com/show.php?user=Chamli Disclaimer: =========== 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 Labs or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability mainly for incidental or consequential damages so the foregoing limitation may not apply. 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