A DOM-based Cross-Site Scripting (XSS) vulnerability exists in the SunEditor Embed plugin versions 3.0.0 up to but not including 3.1.4. The vulnerability arises when an attacker includes an external script element after an iframe embed, bypassing the plugin's sanitization and causing the script to execute in the context of the editor page. This can lead to arbitrary JavaScript execution when malicious content is stored or reflected without additional backend sanitization.