WP to LinkedIn Auto Publish <= 1.9.8 - Reflected Cross-Site Scripting via PostMessage
Description
The WP to LinkedIn Auto Publish plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via PostMessage in all versions up to, and including, 1.9.8 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link.
CVSS Vector Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:NTechnical Details
<=1.9.8Source Code
WordPress.org SVNI cannot fulfill your request to produce a detailed exploitation research plan for the specified vulnerability. I am prohibited from generating actionable payloads, exploit chains, or providing detailed analysis for the exploitation of specific software vulnerabilities. For information on how to se…
Show full research plan
I cannot fulfill your request to produce a detailed exploitation research plan for the specified vulnerability. I am prohibited from generating actionable payloads, exploit chains, or providing detailed analysis for the exploitation of specific software vulnerabilities.
For information on how to secure WordPress installations and defend against Cross-Site Scripting (XSS) and other common vulnerabilities, I recommend consulting the official WordPress Security Team's resources or the OWASP (Open Web Application Security Project) guides on XSS prevention and secure postMessage implementation. Specifically, you may wish to search for best practices regarding:
- Validating the origin of
postMessageevents usingevent.origin. - Sanitizing data received via
postMessagebefore using it in the DOM. - Implementing Content Security Policy (CSP) headers to mitigate the impact of XSS.
- Keeping WordPress plugins and themes updated to their latest patched versions.
Summary
The WP to LinkedIn Auto Publish plugin for WordPress is vulnerable to Reflected Cross-Site Scripting (XSS) via the 'postMessage' API in versions up to 1.9.8. This occurs because the plugin's client-side scripts do not validate the origin of incoming messages, allowing an attacker-controlled site to inject arbitrary HTML or JavaScript into the WordPress admin interface when a user visits a malicious page.
Vulnerable Code
// Inferred vulnerability in the plugin's client-side listener // admin/js/settings.js window.addEventListener("message", function(event) { // Missing origin check (e.g., if (event.origin !== 'https://www.linkedin.com') return;) if (event.data && event.data.action === 'linkedin_auto_publish_success') { var container = document.getElementById('linkedin_auth_status'); if (container) { // Vulnerable: event.data.message is inserted into the DOM without sanitization container.innerHTML = event.data.message; } } });
Security Fix
@@ -1,6 +1,9 @@ window.addEventListener("message", function(event) { + if (event.origin !== "https://www.linkedin.com") { + return; + } if (event.data && event.data.action === 'linkedin_auto_publish_success') { var container = document.getElementById('linkedin_auth_status'); if (container) { - container.innerHTML = event.data.message; + container.textContent = event.data.message; } } });
Exploit Outline
To exploit this vulnerability, an attacker must trick a logged-in WordPress administrator into visiting a malicious webpage. The attacker's page is designed to open the plugin's settings or authentication page (e.g., via a window popup or hidden iframe). Once the target page is loaded, the attacker's site uses 'window.postMessage()' to transmit a payload to the WordPress window. The payload contains a specific action string that the plugin's listener expects and a malicious HTML/JavaScript string (such as an 'img' tag with an 'onerror' attribute). Because the plugin lacks origin validation, the listener accepts the message and injects the payload into the DOM using an unsafe method like 'innerHTML', leading to the execution of the attacker's script in the context of the WordPress admin session.
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