Yahoo! plugs webmail flaw

Yahoo! has fixed a security flaw in its free web-based email service that opened the door to phishing scams, account hijacks and other attacks.

The flaw, known as a cross-site scripting vulnerability, existed because Yahoo!'s website did not detect certain script tags in combination with certain special characters, according to SEC Consult, which issued an advisory on the flaw Friday.

Cross-site scripting flaws are found regularly, including recently in Google's website and earlier this year in Microsoft's Xbox 360 site.

Flaws have also been found on Yahoo!'s site. An attacker could exploit this type of flaw to hijack user accounts, launch information-stealing phishing scams or even download malicious code onto users' computers, experts have said.

A Yahoo! representative said the company fixed the most recent flaws in the "last few weeks" and that its users are protected.

A Yahoo! spokeswoman said: "Yahoo! recently learned of an issue in Yahoo! Mail and worked immediately to begin rollout of a server-side fix which does not require users to take any action.

"We are unaware of any users who were impacted by this issue."

Joris Evers writes for CNET News.com