Stored XSS in Grav Guestbook Plugin

Executive Summary

The Grav Guestbook plugin before version 0.5.2 has a stored cross-site scripting (XSS) vulnerability. This occurs because the plugin's AJAX Load more and Admin Load all handlers insert user-submitted author and message fields into the DOM as unescaped HTML using jQuery. This allows attackers to submit malicious scripts that execute in the browsers of other visitors or administrators.

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Detection Guidance

Check for Grav Guestbook plugin versions before 0.5.2. Inspect network traffic for unescaped HTML submissions in AJAX Load more or Admin Load all handlers. Look for stored author or message fields containing script tags or event handlers.

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Impact Analysis

Unauthenticated attackers can inject scripts that run in other users' browsers, potentially stealing session cookies, redirecting users to malicious sites, or performing actions on their behalf. Administrators using versions 0.5.0 and 0.5.1 may also be affected during moderation sessions.

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Compliance Impact

This vulnerability could lead to unauthorized access to user data, violating GDPR's data protection principles and HIPAA's security requirements for protected health information. It may result in data breaches, non-compliance fines, and reputational damage.

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Mitigation Strategies

Update the Grav Guestbook plugin to version 0.5.2 or later. If updating is not possible, disable the plugin immediately. Implement input validation to sanitize user-submitted content before storage and display.

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