Executive brief
SunEditor is a popular rich-text editor library used in web applications to allow users to create and edit formatted content. A critical vulnerability allows attackers to inject malicious JavaScript code through specially crafted HTML with namespaced tags, bypassing the editor's built-in sanitization. When a victim interacts with the injected element, the hidden JavaScript executes in their browser, enabling attackers to steal credentials, hijack sessions, or perform actions on the victim's behalf.
Technical details
The vulnerability is an XSS (Cross-Site Scripting) vulnerability caused by incomplete sanitization of custom/namespaced HTML elements (e.g., <a:b>). The sanitizer fails to properly strip event-handler attributes (onclick, onmouseover, etc.) from these non-standard tags, leaving executable JavaScript intact. The flaw was introduced in a recent commit that changed the sanitization logic. The attack requires no authentication and is trivial to exploit—an attacker simply needs to inject the malicious payload into the editor content, which will execute when a user interacts with the rendered element. A patch should normalize all elements before sanitization and explicitly handle custom/namespaced tags.
Affected products
- SunEditor SunEditor <=2.47.10
Timeline
- 2026-09-24: disclosed