Today, Adobe posted the Adobe Reader 9.1 and Acrobat 9.1 update, which resolves the recent JBIG2 security issue (CVE-2009-0658), including the 'no-click' variant of the vulnerability. The vulnerability would cause the application to crash and could potentially allow an attacker to take control of the affected system. Adobe said that there are reports that that issue had been exploited.

Adobe recommends users of Adobe Reader and Acrobat 9 update to Adobe Reader 9.1 and Acrobat 9.1. Adobe is planning to make available updates for Adobe Reader 7 and 8, and Acrobat 7 and 8, by March 18. In addition, Adobe plans to make available Adobe Reader 9.1 for Unix by March 25.

Downloads:

Acrobat 9 Standard and Acrobat 9 Pro
http://www.adobe.com/support/downloads/detail.jsp?ftpID=4375
http://www.adobe.com/support/downloads/detail.jsp?ftpID=4382

Acrobat 9 Pro Extended on Windows
http://www.adobe.com/support/downloads/detail.jsp?ftpID=4381

Acrobat 9 Pro users on Macintosh
http://www.adobe.com/support/downloads/detail.jsp?ftpID=4374.