Adobe has issued a security update to patch a code execution vulnerability affecting its Adobe Acrobat and free Adobe Reader applications. According to Adobe's advisory, the vulnerability, if exploited, could crash applications or allow an attacker to take control of the affected system by way of malformed JavaScript code.
If you are using versions 8.0 through 8.1.2 of both Reader and Acrobat or a version older than 7.0.9, you should probably treat this update with the highest possible priority as the flaw is already being exploited by attackers to spread malware in the wild. The latest update is available here for both Microsoft Windows and Mac OS X systems.