A computer security researcher has found a flaw in Microsoft Corp's widely used Internet Explorer browser that he said could let hackers steal credentials to access FaceBook, Twitter and other websites.

He calls the technique "cookiejacking."

"Any website. Any cookie. Limit is just your imagination," said Rosario Valotta, an independent Internet security researcher based in Italy.

Hackers can exploit the flaw to access a data file stored inside the browser known as a "cookie," which holds the login name and password to a web account, Valotta said via email

Once a hacker has that cookie, he or she can use it to access the same site, said Valotta, who calls the technique "cookiejacking."

The vulnerability affects all versions of Internet Explorer, including IE 9, on every version of the Windows operating system.

To exploit the flaw, the hacker must persuade the victim to drag and drop an object across the PC's screen before the cookie can be hijacked.

That sounds like a difficult task, but Valotta said he was able to do it fairly easily. He built a puzzle that he put up on Facebook in which users are challenged to "undress" a photo of an attractive woman.

"I published this game online on FaceBook and in less than three days, more than 80 cookies were sent to my server," he said. "And I've only got 150 friends."

Microsoft said there is little risk a hacker could succeed in a real-world cookiejacking scam.

"Given the level of required user interaction, this issue is not one we consider high risk," said Microsoft spokesman Jerry Bryant.

"In order to possibly be impacted a user must visit a malicious website, be convinced to click and drag items around the page and the attacker would need to target a cookie from the website that the user was already logged into," Bryant said.