Apple's Safari Web browser will give away a user's Mac OS X Address Book data if asked by a malicious Web site.
In a blog post published on Wednesday, Jeremiah Grossman, founder and CTO of WhiteHat Security, reveals that the AutoFill functionality built into Safari 4 and 5 can be triggered remotely using a simple Web form.
AutoFill populates Web forms with frequently entered information, such as the name, address, and e-mail address of the user. Safari's AutoFill preferences menu includes the option to fill out forms "Using info from my Address Book card."
This is checked by default, allowing a malicious Web site operator to obtain the name, street address, and e-mail address listed in the Address Book of a visitor using Safari.
Proof-of-concept exploit code hosted by Robert "RSnake" Hansen, who often collaborates with Grossman on security research, shows how easy it is to obtain this information.
"[The] entire process takes mere seconds and represents a major breach in online privacy," explained Grossman. "This attack could be further leveraged in multistage attacks including e-mail spam, (spear) phishing, stalking, and even blackmail if a user is de-anonymized while visiting objectionable online material."
Grossman said in a comment on his own blog post that he believes the security flaw may reside in the open-source WebKit engine used by Safari and that the flaw may be present in older versions of Google's Chrome browser, which also relies on the WebKit engine.
The proof-of-concept exploit code did not work when tested on Chrome version 5.0.357.99 for the Mac.
Fortunately, the risk is easily mitigated: Users should uncheck the AutoFill option labelled "Using info from my Address Book card."
In the spirit of responsible disclosure, Grossman says he notified Apple about the vulnerability on June 17, 2010. He says that to date, all he has received is an automated reply, leaving him unsure whether the company is actually aware of his report.
Grossman appears not to be the first person to publish information about this privacy flaw. In April 2009, Swiss software developer Patrice Neff demonstrated that the vulnerability could be exploited to obtain a Safari user's birthday from the Mac OS X Address Book. At that time, Safari 5 had not yet been released.
The standards for responsible disclosure were questioned earlier this week by members of Google's security team. Google's security engineers argue that software companies don't move fast enough to protect their users.
For the first six months of 2010, Apple had more vulnerabilities detected in its software than Oracle, Microsoft, HP, Adobe, IBM, VMware, Cisco, Google, or Mozilla, according to a report issued recently by Secunia.