Apple yesterday posted a new support document and sent an email to its security mailing list noting that it is now requiring all OS X users to upgrade to the latest version of the Adobe Flash Player plug-in for Safari to address potential security vulnerabilities.
The company is blocking all older versions Adobe Flash Player prior to 188.8.131.525, and users with an out-of-date version of the plug-in will see messages like "Blocked plug-in" or "Flash out-of-date" when attempting to view Flash content within Safari before updating to the newest version.
For users who are on systems that are not able to run Flash Player 16, there is an update to Flash Player 13 (184.108.40.2069) that addresses the latest vulnerabilities.
APPLE-SA-2015-02-05-1 OS X: Flash Player plug-in blocked
Due to security issues in older versions, Apple has updated the web plug-in blocking mechanism to disable all versions prior to Flash Player 220.127.116.115 and 18.104.22.1689.
The 22.214.171.1245 and 126.96.36.1999 updates were released by Adobe on February 5 to fix a zero-day vulnerability that was being exploited by hackers against Windows machines.