CVE-2025-67849 is a cross-site scripting (XSS) vulnerability identified in Moodle versions 4.5.0, 5.0.0, and 5.1.0. The root cause is improper neutralization of input during web page generation, specifically related to AI prompt responses that are not adequately sanitized before being rendered. This allows an attacker with limited privileges to inject malicious HTML or JavaScript code into Moodle web pages. When other users access these pages, the malicious scripts execute in their browsers within the context of the Moodle domain. This can lead to session cookie theft, enabling attackers to hijack user sessions, or manipulation of the user interface to deceive users or perform unauthorized actions. The vulnerability requires user interaction to trigger the malicious payload and some level of privileges to submit the crafted input, but no authentication bypass is indicated. The CVSS v3.1 base score is 7.3, reflecting high severity due to the ease of network exploitation, low attack complexity, and high impact on confidentiality and integrity. Although no public exploits are known yet, the presence of AI-generated content in Moodle increases the attack surface and risk of exploitation. The vulnerability underscores the importance of rigorous input validation and output encoding, especially when integrating AI-generated content into web applications.

The primary impact of CVE-2025-67849 is on the confidentiality and integrity of Moodle users' data. Successful exploitation can lead to session hijacking, allowing attackers to impersonate legitimate users and access sensitive educational content, personal information, or administrative functions. Manipulation of the user interface can facilitate phishing attacks or unauthorized actions within the platform. For educational institutions and organizations relying on Moodle for e-learning, this can result in data breaches, loss of trust, and disruption of learning activities. While availability is not directly affected, the indirect consequences of compromised accounts and manipulated interfaces can degrade service quality and user confidence. The vulnerability's exploitation could also serve as a foothold for further attacks within the affected networks. Given Moodle's widespread use globally, the impact can be significant if not addressed promptly.

To mitigate CVE-2025-67849, organizations should immediately upgrade Moodle to patched versions once available. In the absence of patches, administrators should implement strict input validation and output encoding on all AI prompt responses before rendering them in web pages. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of XSS attacks. Limit user privileges to the minimum necessary to reduce the risk of malicious input submission. Monitor logs for unusual activities related to AI prompt inputs and user session anomalies. Educate users about the risks of interacting with suspicious content and encourage the use of multi-factor authentication to protect accounts from hijacking. Additionally, consider disabling or restricting AI prompt features temporarily if they cannot be secured promptly. Regular security assessments and penetration testing focused on AI integration points can help identify and remediate similar vulnerabilities proactively.