Google Toolbar flaw opens door for attackers

IDG News Service - Google Inc. said Tuesday that it is working to fix a bug in its Google Toolbar software that could enable cybercriminals to steal data or install malicious software on systems.

The flaw lies in the mechanism for adding custom buttons to the tool bar, according to a blog posting by security researcher Aviv Raff, who issued the first warning about the problem.

Because the tool bar doesn't perform adequate checks when new buttons are being installed, an attacker could spoof the origin of a button and make it appear to be coming from a legitimate Web site, Raff wrote. He added that the attacker then could download malicious files or launch phishing attacks against users who install the button on their tool bars.

Raff also has separately posted proof-of-concept code, showing how such an attack could work with Microsoft Corp.'s Internet Explorer browser.

A Google spokeswoman confirmed that the company is developing a fix for the problem, but she didn't say when flaw is likely to be patched.

Based on the information posted by Raff, an attack seeking to exploit the flaw would require several steps. First, a victim would have to be tricked into clicking on a Web link that would pop up a window asking the user if he wants to install a custom button on his tool bar. Once the button was installed, the victim would have to click on it and then agree to download and run an executable file in order for any malicious software to also be installed.

Because users would have to go through so many steps to fall victim to an attack, the tool bar bug isn't a critical security flaw, said Marc Maiffret, a security researcher who left his former job as chief technology officer at eEye Inc. earlier this month.

"While it is interesting, it's probably a low threat compared to other flaws out there," Maiffret wrote in an instant message. Still, it was sloppy work on Google's part to miss such a simple bug, he added. "They should definitely assess how it slipped through the cracks," he wrote.

This isn't the first Google flaw that Raff has found. Last month, he demonstrated how a simple programming error on Google's Web site could have enabled malicious hackers to launch cross-site scripting attacks.

In that case, Google's programmers didn't properly check HTML code generated by the company's search engine, Raff said. Because of that, he was able to create a specially crafted link that appeared to go to the Google site but would trick the browser of any user who clicked on it into running unauthorized scripting code.

The earlier error was fixed by Google just hours after Raff notified the company of the problem, but a video that shows how the flaw could be exploited can still be viewed on the Web site of security vendor Finjan Inc. Raff works at Finjan, although his Google-related research was done independently of his job responsibilities there.