Google Closes Blogger Security Holes

Google Closes Blogger Security Holes
Kevin Poulsen, SecurityFocus 2003-03-06

Internet search giant Google confirmed this week that it closed several security holes that could have allowed hackers to substitute their own musings for any of the over one-million electronic diaries maintained through the popular "Blogger" online publishing tool.

The vulnerabilities were typical of Web application security weaknesses that have plagued e-commerce sites for years, according to hacker Adrian Lamo, who discovered the holes and passed the details to San Francisco-based Pyra Labs in January. Pyra, creator of Blogger and the related hosting site BlogSpot, was acquired by Google last month.

Lamo demonstrated the most serious vulnerability to SecurityFocus by replacing a reporter's skeletal BlogSpot weblog with one of his own. Before that, the hacker says he tested the technique on two other existing weblogs that had been abandoned, but that he resisted the temptation to replace any of the high profile journals hosted on the site -- one is operated by humorist Dave Barry, another by CNET Radio -- out of respect for the company. "I was tempted to do both of them," says Lamo. "Had Pyra been a less wholesome operation, I might have shown less restraint."

Jason Shellen, Google's associate program manager for Blogger, said details of the vulnerabilities would be posted to Blogger's status page this week.

The hole Lamo demonstrated did not require him to take over an existing weblog. Instead, he bypassed the process BlogSpot used to prevent new customers from establishing weblogs with an address already in use.

After confirming that an address was available, the enrollment application stored it in the user's browser in a hidden form field. A hacker could simply change the name in the form field to the name of an existing weblog to create a new journal that would supercede the legitimate one. "I would characterize it as an outstandingly common problem," says Lamo.

Through similar weakness, the hacker says he could add himself to the list of people authorized to maintain a particular weblog though Blogger, even if they were hosted elsewhere.

Last October, Blogger was shut down for more than two hours after an intruder compromised several user accounts. No billing data or credit card numbers were exposed in that hack, nor by this latest batch of vulnerabilities.