CVE-2019-0859 is a Use-After-Free vulnerability in the system function that handles dialog windows, or more precisely, their additional styles. The exploit pattern found in the wild targeted 64-bit versions of OS, from Windows 7 to the latest builds of Windows 10. Exploitation of the vulnerability allows the malware to download and execute a script written by the attackers, which in the worst-case scenario results in full control over the infected PC.