An annotation engine is the part of a meeting or collaboration app that receives, interprets, and renders drawing, markup, pointer, and overlay input during a live session. It may handle pen strokes on a shared screen, whiteboard notes, stamps, or other participant-generated edits.
In cybersecurity, this component matters because it sits on a trust boundary: it takes data from remote users and turns it into actions on the local client. If the parser or renderer is weak, crafted annotation data can crash the app, corrupt memory, or in severe cases enable remote code execution. Zero-click attacks are especially dangerous here because the target may not need to approve anything; the client processes the hostile input automatically. Defenders reduce risk by patching quickly, limiting who can annotate, disabling the feature in sensitive meetings, and treating collaboration features as part of the attack surface.