Acrobat Reader plug-in vulnerable to attacks

IDG News Service - Security researchers are poring over what one vendor has called a "breathtaking" weakness in the Web browser plug-in for Adobe Systems Inc.'s Acrobat Reader program used to open files in the popular Portable Document Format.

The problem was first highlighted by researchers Stefano Di Paola and Giorgio Fedon, who presented a paper in Berlin last week on security issues related to Web 2.0 technologies such as AJAX (Asynchronous JavaScript and XML).

The Acrobat weakness involves a feature called "open parameters" in the Web browser plug-in for the Reader program.

The plug-in allows arbitrary JavaScript code to run on the client side. The code could include a malicious attack on a computer, wrote Hon Lau on Symantec Corp.'s Security Response weblog.

"The ease in which this weakness can be exploited is breathtaking," Lau wrote. "What this means in a nutshell is that anybody hosting a .pdf, including well-trusted brands and names on the Web, could have their trust abused and become unwilling partners in crime."

Any Web site hosting a PDF file could be manipulated to run an exploit, Lau wrote. Because an exploit is relatively easy to craft, Lau predicted attacks will start until the flaw is fixed.

In their research paper, Di Paola and Fedon wrote that the type of attack used to exploit the problem is called universal cross-site scripting, which uses a flaw in the browser rather than a vulnerability within a Web site. A cross-site scripting attack involves the unintended execution of code as part of a query string contained within a Web site address.

Another Symantec blogger, Zulfikar Ramzan, wrote that attackers can exploit a cross-scripting vulnerability by creating a special URL that points to the Web page. In that address, the attacker would code it to include some of his own content -- such as a form soliciting passwords or credit card information -- that would be displayed on the targeted Web page.

When victims click on the Web address -- which, for example, could be included in a link enclosed in e-mail -- they would be directed to the Web page. If they fill out information on a form on the page, it could be passed to the attacker without the victim knowing the site had been tampered with, Ramzan wrote.

"The result is that the user is lulled into a false sense of security since he trusts the site and therefore trusts any transaction he has with it, even though in reality he is transacting with an attacker," Ramzan wrote.

An Adobe spokesman could not immediately comment.

In highlighting the problem with the Reader plug-in, Di Paola and Fedon warned that Web 2.0 applications -- such as Google Inc.'s Gmail and Google Maps, both of which use AJAX -- will need to be more tightly tied to the security of Web browsers.

Otherwise, the plethora of features in those applications "can be turned into weapons if controlled by a malicious hacker," they wrote.