CVE-2021-24565 in Contact Form 7 Captcha Plugin
Summary
by MITRE • 08/23/2021
The Contact Form 7 Captcha WordPress plugin before 0.0.9 does not have any CSRF check in place when saving its settings, allowing attacker to make a logged in user with the manage_options change them. Furthermore, the settings are not escaped when output in attributes, leading to a Stored Cross-Site Scripting issue.
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Analysis
by VulDB Data Team • 08/26/2021
The vulnerability identified as CVE-2021-24565 affects the Contact Form 7 Captcha WordPress plugin version 0.0.8 and earlier, presenting a critical security risk that combines multiple exploitation vectors. This flaw specifically targets the plugin's administrative settings functionality, where the absence of proper Cross-Site Request Forgery protection creates an avenue for unauthorized modifications to critical configuration parameters. The vulnerability exists within the plugin's settings management interface, where authenticated administrators can be tricked into executing malicious actions without their knowledge or consent, making it particularly dangerous in environments where privileged users frequently access web applications.
The technical implementation of this vulnerability stems from the plugin's failure to implement CSRF tokens during the settings save process, which is a fundamental security control recommended by the Open Web Application Security Project and aligned with CWE-352. Without CSRF protection, attackers can craft malicious requests that appear legitimate to the WordPress administrative interface, allowing them to modify plugin settings through victim sessions. The stored XSS component emerges from the plugin's insufficient output escaping when rendering settings values in HTML attributes, creating a persistent vulnerability that can execute malicious scripts in the context of any user who views the affected administrative pages. This dual nature of the vulnerability places it within the scope of both CWE-352 for CSRF and CWE-79 for cross-site scripting, representing a particularly dangerous combination that can escalate privileges and maintain persistent access.
The operational impact of this vulnerability extends beyond simple configuration tampering, as it provides attackers with the ability to modify critical security settings that could compromise the entire WordPress installation. An attacker who successfully exploits the CSRF component could potentially disable security features, modify CAPTCHA configurations to weaken spam protection, or even inject malicious code through the XSS vector. The stored nature of the XSS vulnerability means that the malicious payload persists in the database and executes whenever administrators access the affected settings pages, making it particularly effective for maintaining long-term access and conducting reconnaissance activities. This vulnerability directly aligns with ATT&CK technique T1078.004 for Valid Accounts and T1547.001 for Registry Run Keys for persistence mechanisms, as it allows for the modification of core plugin configurations that could be leveraged for further exploitation.
Mitigation strategies for CVE-2021-24565 require immediate action including updating the Contact Form 7 Captcha plugin to version 0.0.9 or later, which contains the necessary CSRF protection and output escaping fixes. Administrators should also implement additional security measures such as monitoring for unauthorized configuration changes and conducting regular security audits of WordPress plugins to identify similar vulnerabilities. The remediation process should include verifying that all administrative interfaces properly implement CSRF tokens and that output escaping is consistently applied to all user-supplied data rendered in HTML contexts. Organizations should also consider implementing web application firewalls and security monitoring solutions that can detect and prevent exploitation attempts targeting known WordPress vulnerabilities. The vulnerability highlights the importance of proper input validation and output escaping practices, which are fundamental to preventing both CSRF and XSS attacks according to industry security standards and best practices.