A five-year-old boy who worked out a security vulnerability on Microsoft's Xbox Live service has been officially thanked by the company.

Kristoffer Von Hassel, from San Diego, figured out how to log in to his dad's account without the right password.

Microsoft has fixed the flaw, and added Kristoffer to its list of recognised security researchers.

In an interview with local news station KGTV, Kristoffer said: "I was like yea!"

The boy worked out that entering the wrong password into the log-in screen would bring up a second password verification screen.

Kristoffer discovered that if he simply pressed the space bar to fill up the password field, the system would let him in to his dad's account.

"I got nervous. I thought he was going to find out," Kristoffer told television station, KGTV.

"I thought someone was going to steal the Xbox."

Free games
Dad Robert - who works in security - sent details of the flaw to Microsoft.

In a statement, the company said: "We're always listening to our customers and thank them for bringing issues to our attention.

"We take security seriously at Xbox and fixed the issue as soon as we learned about it."

Kristoffer's name now appears on a page set up to thank people who have discovered problems with Microsoft products.

The company also gave him four free games, $50 (£30), and a year-long subscription to Xbox Live.

Wow amazing, that's pretty cool