Vikunja is an open-source self-hosted task management platform. Starting in version 0.21.0 and prior to version 2.2.0, the Vikunja Desktop Electron wrapper passes URLs from "window.open()" calls directly to "shell.openExternal()" without any validation or protocol allowlisting. An attacker who can place a link with "target="_blank"" (or that otherwise triggers "window.open") in user-generated content can cause the victim's operating system to open arbitrary URI schemes, invoking local applications, opening local files, or triggering custom protocol handlers. Version 2.2.0 patches the issue.