Acrobat flaw could spawn Web attacks

Vulnerability in ubiquitous Acrobat Reader software could be a boon for cybercrooks and spark a rise in Web-based attacks, experts warn.

A security weakness in the ubiquitous Acrobat Reader software could be a boon for cybercrooks, security experts warned Wednesday.

An error in the Web browser plug-in of Adobe Systems' tool lets cybercrooks co-opt the address of any Web site that hosts an Adobe PDF file for use in attacks, Symantec and VeriSign iDefense said. An attacker could construct seemingly trusted links and add malicious JavaScript code that will run once the link is clicked, they said.

For example, an attacker could find a PDF file on a bank Web site and then create a hostile link to that file along with malicious JavaScript, Ken Dunham, director of the Rapid Response Team at VeriSign iDefense, said in a statement.

"This vulnerability makes it possible for cross-site-scripting (XSS) attacks to occur, to steal cookies, session information, or possibly create a XSS worm," he said. XSS attacks put online accounts at risk of hijack and feed information-thieving phishing scams by allowing miscreants to use seemingly trusted links to point to fraudulent Web sites.

The Adobe vulnerability could spark a rise XSS attacks, Symantec said. Such attacks in the past relied on flaws in Web sites, but with the Adobe Reader bug there is now a widely used client-side application that allows cross-site-scripting attacks, it said in an alert sent to users of its DeepSight security intelligence service.

"This development has the potential to significantly change the landscape of conventional cross-site-scripting attacks," Symantec warned. The security problem was disclosed at the Chaos Computer Club conference in Germany over the holidays in a paper by Stafano Di Paola and Giorgio Fedon (click for PDF).

To mitigate the new threat, users can upgrade to Adobe Reader 8, the latest version of the Adobe software released last month, the San Jose, Calif.-based company said in an e-mailed statement. "Adobe is also working on updates to previous versions that will resolve this issue," the company said.

Additionally, users can force PDF files to open in the Acrobat client, not the browser plug-in, Symantec said. VeriSign iDefense suggests removing file type actions within Firefox for PDF, XPDF, FDF and any extension associated with the Adobe Acrobat plug-in.

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