PayPal Patches Critical Security Vulnerabilities


PayPal in the news again for a series of fairly high-profile vulnerabilities discovered by the same guy that found the XSS bugs in Google Calendar and Twitter (Nir Goldshlager).

I’m glad people are looking at PayPal as I’m sure the volume of monetary transactions that pass through their site on a daily basis is huge. It’s still the leading payment processing solution, especially for International transactions.

Seems to be more on the business side rather than effecting users, but exposing so much customer is never a good thing.

A security researcher has uncovered multiple vulnerabilities affecting PayPal, the most critical of which could have enabled attackers to access PayPal’s business and premier reports back-end system.

The vulnerabilities were patched recently by PayPal after security researcher Nir Goldshlager of Avnet Technologies brought the vulnerabilities to the site’s attention. The most critical bug was a permission flow problem in business.paypal.com, and could have potentially exposed a massive amount of customer data.

“An attacker was able to access and watch any other user’s financial, orders and report information with unauthorized access to the report backend application,” Goldshlager explained. “When users have a premier account or business account the transaction details of their orders are saved in the reports application … an attacker can look at any finance reports of premier or business accounts in the PayPal reports application and get a full month [and] day summary of the orders reports.”

That includes information such as the PayPal buyer’s full shipping address, the PayPal transaction ID of the buyer and the date and amount of transaction.

It’s good to see responsible disclosure by the researcher and swift action on behalf of PayPal fixing the flaws. It seems pretty rare these days with the walls of bullshit companies push our via their PR/comms channels try to create enough smoke and mirrors to distract everyone from the real issues.

Hijacking a users account on PayPal is a pretty serious issue as the attacker could simply transfer all the persons funds to their own account, if they weren’t very active they wouldn’t even notice. Even more dangerous if their account is linked to a Credit or Debit card.

The other vulnerabilities Goldshlager found included an XSS (cross-site scripting) vulnerability affecting the paypal.com and business.paypal.com sites that an attacker could use to steal session IDs and hijack user accounts, as well as a CSRF (cross-site request forgery) bug that exposed user account information. The CSRF vulnerability impacts the IPN (Instant Payment Notification) system, a PayPal service that sends a message once a transaction has taken place.

Once IPN is integrated, sellers can automate their back offices so they don’t have to wait for payments to come in to fulfill orders, Goldshlager explained.

“This CSRF exploit method exposes the same information from the buyer as the first vulnerability … to exploit a CSRF attack that adds a Instant Payment Notification access, the attacker will make an attack that adds his own Website address to the victim account IPN settings, and when there is transaction on PayPal the victim’s transaction details will be sent to the attacker’s Website,” he said.

The IPN issue is dangerous too as you could develop some software to place bogus orders on ecommerce sites then generate a fake IPN back to the site to get the goods for free without any actual payment taking place.

Some other minor CSRF flaws were also discovered, but according to Paypal ‘nearly all‘ have been fixed.

Source: eWeek (Thanks to Nir Goldshlager himself for e-mailing me the article)

Posted in: Exploits/Vulnerabilities, Privacy, Web Hacking

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2 Responses to PayPal Patches Critical Security Vulnerabilities

  1. Shyaam April 23, 2010 at 8:34 am #

    Nice Finding…

  2. wow oh wow April 30, 2010 at 5:43 am #

    doods, this is amazing! thanks for the post.