MonsterInsights WordPress Plugin Stored Cross-Site Scripting Vulnerability

A stored cross-site scripting vulnerability has been identified in the MonsterInsights WordPress plugin, affecting versions prior to 8.9.1. The issue arises because the plugin fails to properly sanitize or escape page titles in the top posts/pages section. This flaw allows an unauthenticated attacker to inject arbitrary web scripts into the titles by spoofing requests to Google Analytics.

Impact

Exploitation of this vulnerability allows for stored cross-site scripting, where injected scripts are executed in the context of the user viewing the affected page.

Reproduction

To reproduce this vulnerability, first, open a WordPress page with the MonsterInsights plugin and Google Analytics installed. Search for a non-existent term to trigger a request to Google Analytics that includes the page title in the 'dt' parameter. This request can be intercepted and modified using a tool like Burp Suite. Replace the 'dt' parameter with a URL-encoded script injection payload, such as an image tag with an 'onerror' event. Send enough of these modified requests to the Google Analytics 'collect' endpoint to ensure the injected script appears in the Top Posts/Pages section of the MonsterInsights report after 24 hours.

Remediation

Users are advised to update the MonsterInsights WordPress plugin to version 8.9.1 or later.