In particular, the 9.4.1 release of Acrobat and Reader for Windows and Mac OS X address a publicly disclosed denial of service vulnerability as well as an actively exploited vulnerability that could allow an attacker to take control of the targeted system.
The latter issue also affects Flash Player, which has already been updated.
Existing installations of Acrobat or Reader can most easily be patched by using the programs' built-in update command. Standalone updates for Reader are available for Windows and Mac.
The release of an update for Reader on Unix is planned for November 30.
The next quarterly update for Acrobat and Reader is scheduled for February 8, 2011.