When a user moves one window over another, the open programs don’t know anything about whether their windows should be casting a shadow or having a shadow cast on them, for example. Desktop Window Manager grabs that information from each program’s buffer and creates the overall composite view that the user sees. To understand why Desktop Window Manager is important in a cybersecurity context, consider that programs don’t just draw their windows on the screen they put the necessary information in a buffer. In Microsoft Windows, the component responsible for rendering features such as shadows and transparency is Desktop Window Manager. Windows may overlap, for example, one casting a shadow over others as if it were physically blocking the light. Pretty much everyone is familiar with the windowed interface of modern operating systems: each program opening in a separate window that doesn’t necessarily take up the whole screen.

Microsoft just released the patch, and we suggest applying it immediately. We believe several threat actors have already exploited the vulnerability.

Kaspersky researchers have found a zero-day vulnerability (CVE-2021-28310) in a Microsoft Windows component called Desktop Window Manager (DWM).

Microsoft window manager