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Intro
CVE-2026-47760 is a cross-site scripting (XSS) vulnerability in TinyMCE, an open source rich text editor. It affects all versions from 6.8.0 up to but not including 7.1.0. The root cause lies in improper handling of SVG namespace scope within the HTML sanitizer. Normally, TinyMCE’s sanitizer strips dangerous attributes and scripts from user-supplied content. However, due to a flaw in how SVG namespaces are processed, an attacker can craft a payload that nests elements across different namespaces. This nesting confuses the sanitizer’s attribute filtering logic, allowing malicious event handlers (e.g., onload, onerror) or `javascript:` URIs to survive sanitization. Specifically, by embedding an SVG element inside a foreignObject or other namespace‑aware container, the sanitizer incorrectly applies the wrong scope rules. As a result, attributes that would normally be removed are retained and later executed in the victim’s browser when the editor renders the content. The attack requires the editor to be in a context where it displays untrusted HTML (e.g., user comments, templates). Successful exploitation leads to arbitrary JavaScript execution, potentially stealing cookies, session tokens, or performing actions on behalf of the user. The vulnerability was fixed in version 7.1.0 by correcting the namespace‑aware sanitization logic, ensuring that SVG scopes do not bypass attribute filtering. No public exploits were reported before the patch, but the issue was discovered internally and responsibly disclosed. Users running affected versions should upgrade immediately. Below is the DailyCVE Form summarizing key details.
DailyCVE Form:
Platform: TinyMCE editor
Version: Before 7.1.0
Vulnerability: XSS via SVG
Severity: Critical
Date: 28 May 2026
Prediction: Patched version 7.1.0
What Undercode Say:
Analytics showing related bash commands and PoC codes:
Check installed TinyMCE version (Node.js example) npm list tinymce | grep tinymce Test for vulnerable version range (6.8.0 – 7.0.9) if [[ "$(npm list tinymce --depth=0 | grep -oP 'tinymce@\K[0-9.]+')" =~ ^(6.8.[0-9]|6.9.[0-9]|7.0.[0-9])$ ]]; then echo "VULNERABLE to CVE-2026-47760"; fi Curl test against a demo endpoint (if editor returns raw HTML) curl -X POST https://target.com/submit \ -d 'content=<svg><foreignObject><svg onload=alert(origin)></svg></foreignObject></svg>'
Exploit:
Crafted payload using nested SVG and foreignObject to bypass sanitizer:
<svg xmlns="http://www.w3.org/2000/svg">
<foreignObject>
<svg xmlns="http://www.w3.org/2000/svg" onload="alert('XSS')">
</svg>
</foreignObject>
</svg>
When rendered in TinyMCE (versions <7.1.0), the inner `onload` attribute is not stripped, executing JavaScript.
Protection:
– Upgrade to TinyMCE version 7.1.0 or later immediately.
– If upgrade is not possible, sanitize user input with a strict HTML sanitizer (e.g., DOMPurify) after TinyMCE’s output.
– Disable SVG support via configuration: `extended_valid_elements: ‘svg[!xmlns]’` (not a full fix).
– Apply Content Security Policy (CSP) to block inline script execution.
Impact:
Arbitrary JavaScript execution in the context of the editor’s host page. Leads to session hijacking, data theft, defacement, or forced actions (e.g., CSRF). Affects any application using the vulnerable TinyMCE versions and displaying untrusted rich text. The CVSS score is estimated 8.8 (High) due to low attack complexity and no required privileges.
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Sources:
Reported By: nvd.nist.gov
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