CVE-2024-28593 in Moodle
Summary
by MITRE • 03/22/2024
The Chat activity in Moodle 4.3.3 allows students to insert a potentially unwanted HTML A element or IMG element, or HTML content that leads to a performance degradation. NOTE: the vendor's Using_Chat page says "If you know some HTML code, you can use it in your text to do things like insert images, play sounds or create different coloured and sized text." This page also says "Chat is due to be removed from standard Moodle."
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 04/13/2025
The vulnerability identified as CVE-2024-28593 resides within the Chat activity component of Moodle version 4.3.3, presenting a significant security and performance concern for educational institutions relying on this learning management system. This issue specifically targets the chat functionality where student users can inject HTML content that may lead to unintended consequences beyond the intended chat experience. The vulnerability stems from insufficient input validation and sanitization mechanisms within the chat activity's HTML processing capabilities, allowing malicious or unintended HTML elements to be rendered within the chat interface.
The technical flaw manifests through the acceptance of HTML A elements and IMG elements without proper security controls, creating a potential vector for performance degradation and unauthorized content injection. When students input HTML code into chat messages, the system processes these elements without adequate filtering, potentially allowing for the execution of malicious scripts or the insertion of content that could impact system performance. This vulnerability operates under CWE-79 which categorizes improper neutralization of input during web page generation, specifically addressing cross-site scripting vulnerabilities through HTML injection flaws. The issue represents a direct violation of secure coding practices where user-provided content should never be directly rendered without proper sanitization and validation.
The operational impact of this vulnerability extends beyond simple performance degradation to encompass potential security risks for educational environments. When students can inject HTML content into chat activities, they may inadvertently or maliciously introduce elements that consume excessive system resources, leading to denial of service conditions or degraded user experience. The vulnerability is particularly concerning given that Moodle's documentation acknowledges that chat functionality is slated for removal from standard Moodle installations, suggesting that this issue may persist in legacy systems longer than anticipated. Organizations using Moodle 4.3.3 should consider this vulnerability as a critical risk factor in their security posture, particularly in environments where chat activities remain active and user input is not properly controlled.
Mitigation strategies for CVE-2024-28593 should prioritize immediate implementation of HTML sanitization filters that remove or neutralize potentially dangerous elements before rendering chat content. System administrators should consider implementing content security policies that restrict the execution of inline scripts and external resource loading within chat interfaces. The recommended approach aligns with ATT&CK technique T1203 which focuses on exploitation of remote services through web application vulnerabilities, emphasizing the importance of input validation and output encoding. Organizations should also implement monitoring mechanisms to detect unusual chat activity patterns that might indicate exploitation attempts. Additionally, the most effective long-term solution involves upgrading to newer Moodle versions where this functionality has been properly addressed or removing the chat activity entirely from systems where it is no longer required. The vulnerability serves as a reminder of the importance of maintaining current software versions and implementing proper input validation controls across all web application components, particularly those that process user-generated content.