Feeds

Yahoo! fixes bug that gave free rein to user accounts

All hail the power of the XSS error!

Secure remote control for conventional and virtual desktops

Yahoo! has plugged a site-wide coding error that made it possible for miscreants to gain complete access to a user's account simply by convincing the holder to click on a booby-trapped link.

The security defect is the latest to affect a large website, which consumers and businesses are increasingly entrusting with a plethora of sensitive information, such as email, address books and calendar entries. Yahoo patched the vulnerability, which was the result of a cross-site scripting (XSS) error, hours after the Net Cooties blog first reported it on Thursday.

Researchers say it would have been trivial to exploit the vulnerability because it worked across multiple browsers and required only that a victim click on an innocuous-looking link embedded in an email. Once the link was clicked, an attacker would be able to rummage through the victim's address book, send emails or instant messages posing as the victim, view recent queries and settings made in Yahoo! Maps and access just about every other service on the victim's account.

"Yahoo! takes security seriously and consistently employs measures to help protect our users," a Yahoo! spokesman, who would not let us publish his name, said.

The vulnerability is the latest reminder of the pitfalls of XSS errors, which are often the result of trying to make multiple services scattered across a website work seamlessly. Unlike many other types of web vulnerabilities, an XSS flaw usually is not limited to a particular browser or a small range of unauthorized functions that it can carry out.

"It's incredibly powerful because it allows the attackers to to do anything they want to any website that's vulnerable," says Robert Hansen, a researcher specializing in web-based security who runs the ha.ckers.org blog. "It's not well understood in the development community." Hansen estimates about 80 percent of sites contain one or more XSS flaws.

Two weeks ago, Google fixed an XSS error that could have allowed an attacker to access or delete a Gmail user's messages. It was one of four vulnerabilities discovered that week affecting the search king. One of the other three involved a scripting error that closely resembles an XSS error.

XSS mistakes are painfully easy to make because they rely on javascript that's designed to be rendered on a multitude of browsers and other types of software. Given the flexibility that's needed, javascript often behaves in ways that aren't spelled out in any text book and can only be detected through hours of experimentation.

It would seem XSS bloopers are so common that even those in the business of preventing them sometimes fall victim. Just ask IBM. It turns out a page that supports XSS protections in Big Blue's Quickplace web collaboration tool has its own XSS-related problem that displays the message "Owned" when accessed through this link. (We expect IBM to fix the page, so we took the screenshot below.)

Screenshot of IBM website with message box that says "Owned."

"The moral of the story?" asks Hansen, who credits Arian Evans of Whitehat Security with spotting the blunder. "Make sure to check your site for the vulnerability you claim to be able to prevent in your products."

If there's a silver lining to XSS vulnerabilities, it's the relative ease of fixing them. Plugging flaws in desktop software requires that all affected users upgrade the faulty applications. XSS errors, by contrast, are corrected by fixing code that runs on a server, helping to explain how Yahoo was able to fix this most recent problem so swiftly. ®

New hybrid storage solutions

More from The Register

next story
Israeli spies rebel over mass-snooping on innocent Palestinians
'Disciplinary treatment will be sharp and clear' vow spy-chiefs
Google recommends pronounceable passwords
Super Chrome goes into battle with Mr Mxyzptlk
Infosec geniuses hack a Canon PRINTER and install DOOM
Internet of Stuff securo-cockups strike yet again
THREE QUARTERS of Android mobes open to web page spy bug
Metasploit module gobbles KitKat SOP slop
'Speargun' program is fantasy, says cable operator
We just might notice if you cut our cables
Apple Pay is a tidy payday for Apple with 0.15% cut, sources say
Cupertino slurps 15 cents from every $100 purchase
Snowden, Dotcom, throw bombs into NZ election campaign
Claim of tapped undersea cable refuted by Kiwi PM as Kim claims extradition plot
YouTube, Amazon and Yahoo! caught in malvertising mess
Cisco says 'Kyle and Stan' attack is spreading through compromised ad networks
Hackers pop Brazil newspaper to root home routers
Step One: try default passwords. Step Two: Repeat Step One until success
prev story

Whitepapers

Secure remote control for conventional and virtual desktops
Balancing user privacy and privileged access, in accordance with compliance frameworks and legislation. Evaluating any potential remote control choice.
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.
Providing a secure and efficient Helpdesk
A single remote control platform for user support is be key to providing an efficient helpdesk. Retain full control over the way in which screen and keystroke data is transmitted.