Smokey's Security Weblog

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PayPal XSS Vulnerability Undermines EV SSL Security

A security researcher in Finland has discovered a cross-site scripting vulnerability on paypal.com that would allow hackers to carry out highly plausible attacks, adding their own content to the site and stealing credentials from users.

The vulnerability is made worse by the fact that the affected page uses an Extended Validation SSL certificate, which causes the browser’s address bar to turn green, assuring visitors that the site – and its content – belongs to PayPal. Two years ago, a similar vulnerability was discovered on a different page of the PayPal site, which also used an SSL certificate.

Harry Sintonen discovered the vulnerability and announced it to other web application security specialists in an Internet Relay Chat (IRC) channel today. Sintonen told Netcraft that the issue was critical, adding that, “you could easily steal credentials,” and, “PayPal says you can trust the URL if it begins with https://www.paypal.com,” which is not true in this case.

While SSL certificates do indeed provide a higher level of assurance when it comes to site ownership, they cannot guarantee that a site is free from other security problems – including cross-site scripting. There are concerns that hackers may exploit misunderstandings in the significance of the green address bar for their own benefit, piggybacking off the trust that is instilled by EV certificates. Users need to be aware that a green address bar does not guarantee the origin of a page’s contents if there is a cross-site scripting vulnerability on that page.

Source: Netcraft

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May 17, 2008 - Posted by | Alerts, Friends, Malware, News, Recommended External Security Related Links, Vulnerabilities | , , , , , , ,

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