Adobe has released security updates for Flash Player that address critical vulnerabilities that "could potentially allow an attacker to take control of the affected system." Adobe is aware of "limited, targeted attacks" on OS X, Windows, and Linux.
Adobe lists the affected Flash Player and AIR versions in a security bulletin on its website. Mac or PC users running an affected version should immediately uninstall the web plugin or update their installation to the newest version outlined on Adobe's website.
Apple blocks many older or vulnerable versions of web plugins from functioning, including Adobe Flash and Java, to help limit exposure to potential "zero day" exploits. The web plugins remain blocked in Safari until you install the latest updates. Chrome, Firefox, and most other modern web browser also have web plugin safeguards in place due to the high number of past security risks.