Security Experts:

XSS Flaw Exposed eBay Users to Phishing Attacks

A reflected cross-site scripting (XSS) vulnerability on eBay’s website could have been exploited by malicious actors for phishing attacks, a researcher has demonstrated.

The flaw was identified in December by a researcher who uses the online moniker “MLT.” The expert complained that eBay had not responded to his report for a month, and the e-commerce giant only patched the issue after being contacted by the media.

XSS vulnerabilities are highly common, but that doesn’t make them any less dangerous. A blog post and proof-of-concept (PoC) video published by MLT after the security hole was patched show how an attacker could have exploited the weakness to launch phishing attacks.

The expert has demonstrated how a malicious actor could have created an authentic-looking eBay login page using a freely available tool designed for copying websites from the Internet to the local system.

With the graphics of the eBay login page copied, an attacker simply needed to add a PHP script so that the submitted data would be sent to the attacker’s server instead of eBay.

Once the phishing page was ready, the attacker could have injected it as an iframe into the URL of the vulnerable eBay page. When victims clicked the attacker’s link, they would be presented the legitimate-looking phishing page apparently hosted on the domain.

These types of attacks are dangerous because victims are unlikely to suspect that their credentials have been compromised before malicious actors start abusing the stolen information.

eBay said the researcher followed up with a different email address than the one he used to submit the initial report, which resulted in the delay.

“As a company, we're committed to providing a safe and secure marketplace for our millions of customers around the world. We take reported security issues very seriously, and work quickly to evaluate them within the context of our entire security infrastructure,” eBay told SecurityWeek. “We're aware of this particular issue, which involves fraudsters attempting to phish customers using malicious code in very limited use cases. This type of scheme is extremely rare on our platform. We're continuously adapting our security systems as we become aware of new forms of malicious code, as well as taking the necessary steps to prevent such phishing attempts.”

MLT is not the only researcher who has complained about the time it takes eBay to resolve simple vulnerabilities. In April 2015, a researcher said it took the company more than a year to patch a stored XSS he discovered.

Another stored XSS, this time in eBay’s mobile platform, was found in June 2015 by researcher Cosmin Maier. The expert reported finding a flaw that could have allowed an attacker to force a user’s browser to make a POST request designed to trigger the installation of an app to the victim’s device.

XSS vulnerabilities have also been found recently in several other popular services. In October, Google awarded a researcher over $3,000 for a reflected XSS flaw in YouTube Gaming. In November, LinkedIn patched a persistent XSS in its official Help Center website and, last week, WordPress reported fixing an XSS bug in the content management system (CMS) that could have been exploited to compromise websites.

*Updated with statement from eBay

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.