This indicates an attack attempt to exploit an Use After Free vulnerability in Adobe Flash Player.
The vulnerability is due to an error when the vulnerable software handles a maliciously crafted SWF file. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted SWF file.
Adobe Flash Player Desktop Runtime 184.108.40.2066 and earlier for Windows and Macintosh
Adobe Flash Player Extended Support Release 220.127.116.119 and earlier for Windows and Macintosh
Adobe Flash Player for Google Chrome 18.104.22.1686 and earlier for Windows, Macintosh, Linux and ChromeOS
Adobe Flash Player for Microsoft Edge and Internet Explorer 11 22.214.171.1246 and earlier for Windows 10
Adobe Flash Player for Internet Explorer 11 126.96.36.1996 and earlier for Windows 8.1
Adobe Flash Player for Linux 188.8.131.529 and earlier for Linux
AIR Desktop Runtime 184.108.40.2060 and earlier for Windows and Macintosh
AIR SDK 220.127.116.110 and earlier for Windows, Macintosh, Android and iOS
AIR SDK & Compiler 18.104.22.1680 and earlier for Windows, Macintosh, Android and iOS
AIR for Android 22.214.171.124 and earlier for Android
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.