Software Engineering Institute

eBay is a popular auction web site. When an eBay user posts an auction, eBay allows SCRIPT tags to be included in the auction description. This creates a cross-site scripting vulnerability in the eBay website. More information about cross-site scripting is available in CERT Advisory CA-2000-02.

An attacker may be able to obtain sensitive data from the eBay web site. As of the publication of this document, attackers are using this vulnerability to redirect auction viewers to phishing sites and to modify the eBay auction page to steal credentials. A wide range of impacts may be possible, including disclosure of passwords, credit card numbers, or other personal information. Likewise, information stored in cookies could be stolen or corrupted. An attacker could also exploit web browser vulnerabilities that require scripting support.

We are currently unaware of a practical solution to this problem, however the following workarounds may help mitigate the vulnerability:

Disable scripting

Disable scripting in your web browser, as specified in the Securing Your Web Browser document and the Malicious Web Scripts FAQ. This can also be accomplished by adding "ebay.com" to the Restricted Sites zone in Internet Explorer. Users of Mozilla-based browsers can use Configurable Security Policies (CAPS) to disable scripting for the "ebay.com" web site.

Validate web site addresses

When interacting with web sites, pay close attention to the web site address displayed by the browser. Especially when providing login information, make sure the web browser is displaying the proper URL, as described in the eBay Spoof Email Tutorial and US-CERT Cyber Security Tip ST04-014.

Validate web site certificates

Web sites may require sensitive information such as passwords or credit card information. In these cases, make sure the web site is using an encrypted (HTTPS) connection. Validate the web site certificate, as described in US-CERT Cyber Security Tip ST05-010.