LastPass Password Service Patches Cross-Site Scripting Flaw

Despite the convenience of a cloud-based password management service, a security researcher found a cross-site scripting vulnerability in LastPass that could compromise user account data.

Despite the convenience of a cloud-based password management service, a security researcher warned that putting passwords in the cloud may not be the best idea after all.

After the Gawker breach revealed the number of people reusing passwords across multiple sites, there was renewed interest in using password management applications such as KeePass and LastPass.

Instead of writing down all the passwords for each Website and program on a Post-It or saving it as a text file on the computer, the services allow users to enter the login credentials and secure them with a strong master password.

The user logs into the LastPass account and clicks on which site to log into, and the LastPass browser plug-in handles the actual login process using the stored credentials. However, there was a cross-site scripting flaw in LastPass that allowed attackers to see the user's e-mail address, password reminder information, the list of Websites associated with the user and login history for each site, said Mike Cardwell, a United Kingdom-based security researcher. The login history included sites logged into, time and dates of the login attempt, and the originating IP address, he said.

While he didn't achieve "the holy grail" to grab passwords, "I'm convinced it can be done," he said.

Cardwell notified LastPass of the vulnerability, which fixed the flaw within three hours, according to the LastPass blog. The problem was "with our testing procedure for this particular case," the company said. While "disappointed" at missing the case, the company was confident the resulting fixes will "lead to an even stronger product in the near term."

The company claimed no one has successfully exploited the flaw "beyond the person who found it," and no client data was impacted. The flaw could have been exploited only if the user visited a malicious site set up to exploit the flaw while still logged into LastPass, the company wrote.

LastPass customers should "still be very concerned," Cardwell said. "I believe this is ultimately a problem with their architecture and something which could easily happen again in future," he said.

The company addressed some of Cardwell's concerns, such as implementing HSTS (HTTP Strict Transport Security) protocol to ensure Chrome and Firefox will maintain the SSL connection as long as the user is on a LastPass page. Without HSTS, it was possible for a man-in-the-middle attack to create a fake page and trick the browser into fetching it by using an iframe, Cardwell said.

LastPass was implementing "something very similar" to CSP (Content Security Policy), the company said. Developed by Mozilla, CSP allows Web designers and administrators to control how content is displayed on the site. CSP is a "big step forward" in defending against this kind of attack, according to the company.

The company also implemented X Frame Options, which would make an attack like this more difficult to exploit as "it makes it impossible" for the LastPass pages to be embedded in another page using an iFrame.

Despite having closed the security hole, concerned users can stay safe by logging out of LastPass before heading over to a site with questionable or adult-related content, LastPass suggested.

"Perhaps it's just inherently dangerous to outsource your password management to a third party," Cardwell said.