SunEditor is a lightweight and powerful WYSIWYG editor in vanilla JavaScript with no dependencies. Prior to 3.1.4, the SunEditor Embed plugin in src/plugins/modal/embed.js parses attacker-controlled raw embed HTML with DOMParser and processes the resulting DOM nodes. When an external script element follows a valid iframe, the plugin recreates a script element from the attacker-controlled src attribute and appends it to the live DOM, causing JavaScript execution in the editor page. If an application stores or reflects SunEditor content without additional backend sanitization, an attacker who can submit embed HTML can trigger stored or reflected cross-site scripting when another user opens, previews, renders, or edits the content, enabling access to page data and account actions as the victim. This issue is fixed in version 3.1.4.