PayPal Patches Critical Security Vulnerabilities

PayPal says it has closed a number of security holes uncovered by an Avnet Technologies security researcher, including one that could have allowed an attacker to access PayPal's back-end system for business and premier account reports and acquire a mountain of data.

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, 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.

The other vulnerabilities Goldshlager found included an XSS (cross-site scripting) vulnerability affecting the and 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.

Goldshlager also uncovered smaller CSRF issues, he said. He reported the bugs to the site in February. According to PayPal, nearly all the problems Goldshlager uncovered were fixed right away.

"As you know, these types of security issues are very complex and we are grateful for our strong working relationship with the security researcher as well our partnership with the security community that have brought these issues to light," a PayPal spokesperson told eWEEK in an e-mail. "We have a shared mission to make PayPal and the Internet as safe as possible for our customers."