Skype plugs critical cross-zone scripting hole

But researcher not quite ready to give patch the thumbs-up

Skype this week patched a critical vulnerability that forced it to dump several features from its VoIP and chat software to prevent attackers from hijacking Windows PCs.

In a security advisory issued Tuesday, Skype said it fixed the underlying flaw publicized by Israeli researcher Aviv Raff nearly three weeks ago. The vulnerability, which Raff called a cross-zone scripting bug, could be exploited with rigged video files that leveraged a security flaw in how Skype rendered HTML.

At root, Raff said, was the fact that Skype, which uses IE's Web control to handle internal and external HTML pages, ran the control in a low-security mode. "Skype is running this Web control in Local Zone ... [and] the HTML pages in a not-locked Local Zone mode," Raff said in mid-January.

After Raff and others posted proof-of-concepts, Skype temporarily plugged the hole by first ditching connections to Dailymotion, one of the Internet-calling service's video-sharing partners. Six days later, it severed the line to Metacafe, another partner, when Raff pointed out an even more serious exploit.

Last week, Raff spotted yet another Skype problem, this time in the SkypeFind command, which lets users recommend businesses to others and write reviews of those businesses. At the time, Raff said if a hacker crafted a review that included a malicious script, any user who viewed the business via the SkypeFind command would have his PC shanghaied.

Raff traced all three cross-zone scripting vulnerabilities to Skype's poor security model, and said a fix was relatively simple. "To lock the Local Zone, they basically need to change one registry value," he said last Thursday.

Skype hinted that it had done just that. "The core vulnerability has been fixed by setting IE control security context to Internet Zone," said the company in Tuesday's security alert. It also claimed that all three of the exploits -- the two related to Dailymotion and Metacafe and the third connected to SkypeFind -- had been quashed by the patched Skype now available for download.

Raff, however, wasn't willing to give it the thumbs up, at least not yet. After seeing the Skype advisory, he had questions that needed answering before he would give the patch a green light. "I'm still waiting for answers from Skype," Raff said in an instant message interview.

Users can download the patched Skype -- Windows version 3.6.0.248 -- from the service's Web site. Existing Skype users can update by using the software's "Check for Updates" command under the Help menu.

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Gregg Keizer

Computerworld
Show Comments

Father’s Day Gift Guide

Brand Post

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Luke Hill

MSI GT75 TITAN

I need power and lots of it. As a Front End Web developer anything less just won’t cut it which is why the MSI GT75 is an outstanding laptop for me. It’s a sleek and futuristic looking, high quality, beast that has a touch of sci-fi flare about it.

Emily Tyson

MSI GE63 Raider

If you’re looking to invest in your next work horse laptop for work or home use, you can’t go wrong with the MSI GE63.

Laura Johnston

MSI GS65 Stealth Thin

If you can afford the price tag, it is well worth the money. It out performs any other laptop I have tried for gaming, and the transportable design and incredible display also make it ideal for work.

Andrew Teoh

Brother MFC-L9570CDW Multifunction Printer

Touch screen visibility and operation was great and easy to navigate. Each menu and sub-menu was in an understandable order and category

Louise Coady

Brother MFC-L9570CDW Multifunction Printer

The printer was convenient, produced clear and vibrant images and was very easy to use

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Featured Content

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?