This is hot off the press: Adobe recommends that you upgrade your Adobe Acrobat 9 or Adobe Reader 9 installation to 9.1: Security Updates available for Adobe Reader 9 and Acrobat 9
Here is what Adobe has to say (among other things) about this patch: “Adobe categorizes this as a critical issue and recommends that users apply the update for their product installations.” More information is available on the page I linked to.
Upgrade! Really!