For instance, the recently uncovered Flash bug has been actively exploited in attacks against Adobe Reader for a few weeks now. From the Adobe Product Security Incident Response Team (PSIRT) blog:
Today, a Security Bulletin (APSB10-28) has been posted regarding security releases for Adobe Reader and Acrobat. The updates address critical security issues in the products, including CVE-2010-3654 noted in Security Advisory APSA10-05 and CVE-2010-4091 referenced in the Adobe PSIRT blog ("Potential issue in Adobe Reader"), as well as the vulnerabilities addressed in the November 4 Adobe Flash Player update as noted in Security Bulletin APSB10-26. Adobe recommends that users apply the updates for their product installations.
Note that today's updates represent and out-of-cycle release. The next quarterly security updates for Adobe Reader and Acrobat are scheduled for February 8, 2011.
It's important to note that these vulnerabilities affect multiple platforms, from Adobe's security bulletin:
Critical vulnerabilities have been identified in Adobe Reader 9.4 (and earlier versions) for Windows, Macintosh and UNIX, and Adobe Acrobat 9.4 (and earlier 9.x versions) for Windows and Macintosh. These vulnerabilities could cause the application to crash and potentially allow an attacker to take control of the affected system.
If you haven't yet, update to Adobe Reader 9.4. If you'd like more information, see Adobe's Security Bulletin APSB10-28. For my security and technology observations throughout the day, find me on Twitter.