A zero-day vulnerability in yahoo.com that lets attackers hijack Yahoo!
email accounts and redirect users to malicious Web sites offers a fascinating glimpse into the underground market for large-scale exploits.
The exploit, being sold for $700 by an Egyptian hacker
on an exclusive cybercrime forum, targets a “cross-site scripting” (XSS) weakness in yahoo.com that lets attackers steal cookies from Yahoo! Webmail users. Such a flaw would let attackers send or read email from the victim’s account. In a typical XSS attack
, an attacker sends a malicious link to an unsuspecting user; if the user clicks the link, the script is executed, and can access cookies, session tokens or other sensitive information retained by the browser and used with that site. These scripts can even rewrite the content of the HTML page.
The hacker posted the following video to demonstrate the exploit for potential buyers. I’ve reproduced it and published it to youtube.