CVE-2026-47760: 
JavaScript vulnerability analysis and mitigation

CVE-2026-47760 is a Cross-Site Scripting (XSS) vulnerability in TinyMCE, an open-source rich text editor, caused by improper SVG namespace scope handling in its sanitizer. Affected versions span from 6.8.0 up to (but not including) 7.1.0, covering packages distributed via npm, NuGet, and Composer. The vulnerability was first published on May 20, 2026, by researcher maple3142 of DEVCORE, with NVD publication on May 28, 2026. The GitHub Advisory (GHSA-mh5m-5hw4-5c69) assigns a CVSS v3.1 score of 8.7 (High), while the NVD entry records a score of 5.4 (Medium) (GitHub Advisory, TinyMCE Advisory).

The root cause is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation — Cross-Site Scripting), specifically arising from incorrect SVG namespace scope handling within TinyMCE's HTML sanitizer. When processing nested SVG elements, the sanitizer fails to correctly track namespace context, allowing a crafted payload to smuggle malicious attributes past the sanitization layer and execute arbitrary JavaScript. Exploitation requires the attacker to have low-level authenticated access to submit content through the TinyMCE editor, and a victim user must interact with (view) the maliciously crafted content. The fix was introduced in TinyMCE 7.1.0 through a rewrite of the vulnerable sanitization code (TinyMCE Advisory, GitHub Advisory).

Successful exploitation allows an authenticated attacker with low privileges to inject and execute arbitrary JavaScript in the browsers of other users who view the malicious content. The scope change (S:C in CVSS) indicates the impact extends beyond the TinyMCE component itself to the broader browser context, enabling session hijacking, credential theft, or unauthorized actions on behalf of victims. Confidentiality and integrity are both rated High in the GitHub advisory's scoring, reflecting the potential for significant data exposure and content manipulation, while availability is not directly impacted (GitHub Advisory, TinyMCE Advisory).

As of the time of reporting, there is no public proof-of-concept exploit and no evidence of active in-the-wild exploitation (Feedly). The EPSS score is approximately 0.033% (10th percentile), indicating a low near-term probability of exploitation. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. No threat actor attribution has been reported.

1. Identify a target: Locate a web application using TinyMCE versions 6.8.0–7.0.x (npm, NuGet, or Composer packages) where authenticated users can submit rich text content.
2. Authenticate: Obtain low-privilege credentials to access the TinyMCE editor interface on the target application.
3. Craft a malicious payload: Construct an HTML payload leveraging nested SVG elements that exploit the namespace scope mishandling in TinyMCE's sanitizer. The nesting causes the sanitizer to incorrectly evaluate attribute context, allowing event handler attributes (e.g., onload, onerror) to survive sanitization.
4. Submit the payload: Insert the crafted SVG payload into a TinyMCE-powered content field (e.g., a blog post, comment, or profile field) and save or publish it.
5. Trigger execution: When another user (e.g., an administrator or another authenticated user) views the page containing the malicious content, the injected JavaScript executes in their browser context, enabling session token theft, phishing redirects, or further exploitation (TinyMCE Advisory, GitHub Advisory).

• Network: Unusual outbound requests from victim browsers to attacker-controlled domains following interaction with TinyMCE-rendered content; unexpected POST requests exfiltrating session cookies or tokens.
• Logs: Web server or application logs showing submission of content containing nested <svg> elements with suspicious attribute patterns (e.g., onload, onerror, javascript: URIs) to TinyMCE-backed endpoints.
• File System / Database: Stored content in the application database containing obfuscated or encoded nested SVG payloads with event handler attributes that should have been stripped by the sanitizer.
• Browser / Client-Side: Unexpected JavaScript execution errors or network requests originating from pages rendering TinyMCE content; browser developer tools showing script execution from inline SVG elements.

The vulnerability is fixed in TinyMCE 7.1.0, which rewrites the vulnerable sanitization code; all users of versions 6.8.0 through 7.0.x should upgrade immediately across all package managers (npm, NuGet, Composer) (TinyMCE Advisory). No official workaround is provided by the vendor. As a compensating control where immediate patching is not feasible, deploying strict Content Security Policy (CSP) headers — restricting inline script execution and limiting script sources to trusted domains — can reduce the risk of successful JavaScript execution (Feedly).

The vulnerability was discovered and responsibly disclosed by maple3142 of DEVCORE, a well-regarded security research firm, and Tiny (the TinyMCE maintainer) acknowledged their contribution in the advisory (TinyMCE Advisory). Coverage has appeared on security aggregation sites including SecurityOnline.info and CVEReports.com, and the vulnerability was noted on social media platforms such as Bluesky. Overall community reaction has been measured, consistent with the absence of active exploitation and the availability of a straightforward patch.