This indicates an attack attempt to exploit a 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 affected application, via a crafted SWF file.
Adobe Flash Player Desktop Runtime 220.127.116.11 and earlier on Windows and Macintosh
Adobe Flash Player Extended Support Release 18.104.22.1681 and earlier on Windows and Macintosh
Adobe Flash Player for Google Chrome 22.214.171.124 and earlier on Windows, Macintosh and Linux
Adobe Flash Player for Microsoft Edge and Internet Explorer 11 126.96.36.199 and earlier on Windows 10
Adobe Flash Player for Internet Explorer 10 and 11 188.8.131.52 and earlier on Windows 8.0 and 8.1
Adobe Flash Player for Linux 184.108.40.2068 and earlier on Linux
AIR Desktop Runtime 220.127.116.11 and earlier on Windows and Macintosh
AIR SDK 18.104.22.168 and earlier on Windows, Macintosh, Android and iOS
AIR SDK & Compiler 22.214.171.124 and earlier on Windows, Macintosh, Android and iOS
AIR for Android 126.96.36.199 and earlier Android
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.