http://www.adobe.com/support/security/bulletins/apsb09-06.html
A critical vulnerability has been identified in Adobe Reader 9.1 and Acrobat 9.1 and earlier versions. This vulnerability (CVE-2009-1492) would cause the application to crash and could potentially allow an attacker to take control of the affected system. A second vulnerability has also been reported that appears to affect Adobe Reader for UNIX only (CVE-2009-1493).
Adobe recommends users of Adobe Reader 9.1 and Acrobat 9.1 and earlier versions update to Adobe Reader 9.1.1 and Acrobat 9.1.1. Adobe recommends users of Acrobat 8 update to Acrobat 8.1.5, and users of Acrobat 7 update to Acrobat 7.1.2. For Adobe Reader users who can’t update to Adobe Reader 9.1.1, Adobe has provided the Adobe Reader 8.1.5 and Adobe Reader 7.1.2 updates.