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 application, via a crafted SWF file.
Adobe Flash Player Desktop Runtime 126.96.36.199 and earlier on Windows and Macintosh
Adobe Flash Player Extended Support Release 188.8.131.526 and earlier on Windows and Macintosh
Adobe Flash Player for Google Chrome 184.108.40.206 and earlier on Windows, Macintosh and Linux
Adobe Flash Player for Internet Explorer 10 and Internet Explorer 11 220.127.116.11 and earlier on Windows 8.0 and 8.1
Adobe Flash Player 18.104.22.1688 and earlier on Linux
AIR Desktop Runtime 22.214.171.124 and earlier on Windows and Macintosh
AIR SDK 126.96.36.199 and earlier on Windows, Macintosh, Android and iOS
AIR SDK & Compiler 188.8.131.52 and earlier on Windows, Macintosh, Android and iOS
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.