This indicates an attack attempt to exploit a Remote Code Execution vulnerability in Adobe Flash Player.
The vulnerability is due to an input validation error in the RTMP protocol. A remote attacker can exploit this to execute arbitrary code within the context of the application.
Adobe Flash Player 188.8.131.52 and earlier versions for Windows, Macintosh and Linux operating systems
Adobe Flash Player 184.108.40.206 and earlier versions for Android 4.x, and Adobe Flash Player 220.127.116.11 and earlier versions for Android 3.x and 2.x
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.