How exploitable is this vulnerability in practice?

The vulnerability is highly exploitable when users regularly authorize MCP OAuth clients, as an attacker only needs to register a malicious client and wait for a victim to authorize and a second user to revoke it. Once the toast notification appears, clicking the rendered link can execute attacker-supplied JavaScript in the victim's browser.

Does an attacker need authenticated access to exploit this issue?

No. The attacker can be unauthenticated to register a malicious MCP OAuth client but relies on authenticated n8n users to complete the authorization and revocation steps. The actual XSS executes in an authenticated user's session, giving the attacker their effective privileges.

What is the safest general fix pattern for developers?

Apply strict, context-aware encoding to all user-controlled fields before rendering them into the UI and avoid injecting raw HTML or text directly into components. Centralize notification and message rendering through a small number of well-reviewed helpers that enforce escaping and disallow arbitrary markup or script execution.

Severity:

CRITICAL RISK

(9.6)

Stored Cross-Site Scripting (CWE-79) in n8n MCP OAuth Client Name Handling

CVE-2026-42235

Published:

May 4, 2026

Status:

Analyzed

Summary

Affected Context

Exploit Preconditions

Why This Happens

Potential Impact

General Mitigation Guidance

How Teams Detect Issues Like This

Frequently Asked Questions

Source

NDV

Recent Vulnerabilities

CWE-918

HIGH RISK

HIGH

(8.6)

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Unauthorized Access to Internal Resources via SSRF

May 6, 2026

CWE-863

HIGH RISK

HIGH

(8.8)

Authorization Bypass (CWE-863) in OpenClaw Matrix Room Control Commands

Privilege Escalation via Bypassed Access Control

May 6, 2026

Vulnerability Type

Category:

Cross-Site Scripting (XSS)

CWE:

CWE-79;CWE-87

Impact:

Account Takeover and Workflow Manipulation via Stored XSS

Severity:

CRITICAL RISK

(9.6)

CVSS Version:

3.1

Vulnerability Type

Category:

Cross-Site Scripting (XSS)

CWE:

CWE-79;CWE-87

Impact:

Account Takeover and Workflow Manipulation via Stored XSS

Severity:

CRITICAL RISK

(9.6)

CVSS Version:

3.1

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Stored Cross-Site Scripting (CWE-79) in n8n MCP OAuth Client Name Handling

Summary

Affected Context

Exploit Preconditions

Why This Happens

Potential Impact

General Mitigation Guidance

How Teams Detect Issues Like This

Frequently Asked Questions

Source

Recent Vulnerabilities

HIGH RISK

HIGH

(8.6)

Server-Side Request Forgery (CWE-918) in OpenClaw Zalo Plugin sendPhoto

HIGH RISK

HIGH

(8.8)

Authorization Bypass (CWE-863) in OpenClaw Matrix Room Control Commands

Vulnerability Type

Vulnerability Type

Vulnerability Type

Catch This CVE While Code Is Being Written

Ship clean & secure code faster

Ship clean & secure code faster

Ship clean & secure code faster

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