Security Experts:

Yahoo Exploit Up For Grabs - Millions Potentially At Risk Over $700

On Friday, reporter Brian Krebs published a report on a different kind of post-holiday sale, one where a seller is looking to make a quick buck and expose millions of email accounts to compromise. According to Krebs, an Egyptian hacker is selling access to Cross-Site Scripting (XSS) vulnerability in Yahoo for the sum of $700 USD.

According to the story, a post on the Darkcode forum announced the XSS flaw, and provided video proof (embedded below) of it working. However, since the initial post on Friday, several other underground forums have started circulating the same video, and there is talk that the XSS vulnerability itself isn’t legit – based mainly on the sale price.

The common thought is that the flaw itself is worth three-times as much as the asking price, leading to the thought that it is either fake or doesn’t work. Still, criminals selling off valuable exploits at rock bottom prices isn’t anything new, and once sold and used, it’s likely that the flaw will be patched quickly.

“I’m selling Yahoo stored xss that steal Yahoo emails cookies and works on ALL browsers. And you don’t need to bypass IE or Chrome xss filter as it do that itself because it’s stored xss. Prices around for such exploit is $1,100 – $1,500, while I offer it here for $700. Will sell only to trusted people cuz [sic] I don’t want it to be patched soon,” the advertisement on Darkcode says.

Krebs spoke to Ramses Martinez, the director of security at Yahoo, who said that once they figure out where the XSS flaw, new code can be deployed and the issue resolved in a matter of hours. The problem is that Yahoo’s URL base is so vast; it isn’t clear where the vulnerability originated from, and if it impacts a single application or function, or if it is chained across several areas.

Related: Recently-Patched HTML Sanitization Flaw Linked to Hotmail XSS Vulnerability

For now, the XSS flaw is still for sale. Whether or not it sells is anyone’s guess. Yahoo has other XSS related issues, more than a dozen of them in fact. A list of all outstanding XSS flaws on Yahoo can be seen here.

Related: Crossing XSS Off Your Threat Landscape

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Steve Ragan is a security reporter and contributor for SecurityWeek. Prior to joining the journalism world in 2005, he spent 15 years as a freelance IT contractor focused on endpoint security and security training.