CVE-2021-24740 in Tutor LMS Plugin
Summary
by MITRE • 10/18/2021
The Tutor LMS WordPress plugin before 1.9.9 does not escape some of its settings before outputting them in attributes, which could allow high privilege users to perform Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed.
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Analysis
by VulDB Data Team • 10/22/2021
The vulnerability identified as CVE-2021-24740 affects the Tutor LMS WordPress plugin version 1.9.8 and earlier, representing a critical cross-site scripting weakness that undermines the security posture of affected WordPress installations. This flaw specifically resides in the plugin's handling of user settings where insufficient output escaping occurs in HTML attributes, creating an avenue for malicious code injection that can persist across user sessions.
The technical implementation of this vulnerability stems from the plugin's failure to properly sanitize and escape user-controllable data before rendering it within HTML attributes. When high-privilege users access certain administrative interfaces within the Tutor LMS plugin, the system processes and displays configuration values without adequate HTML escaping mechanisms. This oversight allows attackers with capabilities such as administrator or editor roles to inject malicious JavaScript code that executes in the context of other users' browsers when they view affected pages.
This vulnerability operates under the broader context of CWE-79 which classifies improper neutralization of input during web page generation, specifically targeting cross-site scripting scenarios. The flaw's exploitation requires an attacker to possess a high privilege level within the WordPress environment, typically corresponding to roles with the unfiltered_html capability or equivalent administrative access. However, the vulnerability's impact extends beyond the immediate user session as the malicious payloads can persist and execute whenever affected pages are rendered, creating a sustained threat vector.
The operational impact of CVE-2021-24740 is significant for organizations relying on Tutor LMS for educational platform management, as it enables attackers to potentially execute arbitrary code, steal user sessions, perform actions on behalf of authenticated users, or redirect victims to malicious websites. The vulnerability particularly affects environments where the unfiltered_html capability is restricted as a security measure, making the attack surface more expansive for privileged users who may not realize the extent of their exposure.
Mitigation strategies for this vulnerability involve immediate patching of the Tutor LMS plugin to version 1.9.9 or later, which implements proper output escaping mechanisms for all user-controllable settings. Security administrators should also conduct thorough reviews of all installed WordPress plugins to identify similar output escaping vulnerabilities, particularly in administrative interfaces where user input is processed. The implementation of Content Security Policy headers can provide additional defense-in-depth measures, while regular security audits of WordPress installations should include assessment of plugin output sanitization practices. Organizations should also consider implementing automated monitoring solutions to detect anomalous user behavior patterns that might indicate exploitation attempts.
The ATT&CK framework categorizes this vulnerability under T1548.003 for Abuse of Functionality, where attackers leverage legitimate administrative capabilities to execute malicious code. The vulnerability's persistence and the fact that it operates within the context of privileged users aligns with techniques for maintaining access and escalating privileges within compromised environments. Security teams should also consider the broader implications for WordPress security hygiene, as this vulnerability demonstrates how seemingly minor output escaping oversights can create significant security risks in web applications.