You can check your version of FLASH at:
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…from Apple


Date: Thu, 28 Apr 2016 15:05:32 -0700
From: Apple Product Security
Subject: APPLE-SA-2016-04-28-1 OS X: Flash Player plug-in blocked

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APPLE-SA-2016-04-28-1 OS X: Flash Player plug-in blocked

Due to security and stability issues in older versions, Apple 
has updated the web plug-in blocking mechanism to disable all
versions prior to Flash Player 21.0.0.226 and 18.0.0.343.

Information on blocked web plug-ins will be posted to:
http://support.apple.com/en-us/HT202681

This message is signed with Apple's Product Security PGP key,
and details are available at:
https://www.apple.com/support/security/pgp/
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