Adobe Patches Acrobat And Reader XSS Bug, 3 Other Flaws

A week after acknowledging a serious flaw in older versions of its popular Acrobat and Reader software, Adobe patched multiple bugs to stop attackers from piggybacking malicious code on trusted PDF files and grabbing control of computers.

The four fixed flaws include a cross-site scripting (XSS) bug that one researcher last week said had the potential to be the "number one worst vulnerability of 2007." Three others, all which were rated as "critical" by Adobe, were also patched with new versions of Acrobat and Reader. According to Adobe, two of the three would let criminals take complete control of a victimized computer running Windows, Mac OS X, or Linux by getting its user to open a malformed PDF; the third could crash the applications in a denial-of-service attack.

The company also posted a second security advisory related to the XSS bug; the bulletin spelled out techniques that Microsoft IIS and Apache Web server users could take on the server side to block cross-site scripting attacks.

Although the current versions 8.0 of Adobe Acrobat and Reader do not contain any of the four fixed flaws -- earlier, Adobe had recommended that users update to v. 8.0 -- it posted the 7.0.9 update for those who were not able to shift to the newest edition. "Adobe Reader 7 users who wish to stay with their current version can follow the instructions for a solution as outlined in the bulletin," a company spokesman said in an e-mail.

Windows, Mac OS X, and Linux versions of the 7.0.9 Acrobat and Reader updates can be downloaded from the Adobe Web site; a patch is available for Mac OS X users who want to update from 7.0.8 without having to download and install the entire application.

Updates to Adobe Acrobat and Adobe Reader 6.x, which is also vulnerable to the cross-site scripting bug, will be forthcoming, said the company's spokesman, and should be available "soon."