CVE-2021-24286 in Redirect 404 to Parent Plugin
Summary
by MITRE • 05/14/2021
The settings page of the Redirect 404 to parent WordPress plugin before 1.3.1 did not properly sanitise the tab parameter before outputting it back, leading to a reflected Cross-Site Scripting issue
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Analysis
by VulDB Data Team • 05/03/2025
The vulnerability identified as CVE-2021-24286 affects the Redirect 404 to parent WordPress plugin, specifically targeting versions prior to 1.3.1. This issue stems from inadequate input validation within the plugin's settings page implementation, creating a security exposure that allows malicious actors to exploit reflected cross-site scripting vulnerabilities. The flaw manifests when the plugin processes the tab parameter without proper sanitisation, enabling attackers to inject malicious scripts that execute in the context of authenticated users' browsers. This vulnerability resides within the plugin's user interface handling mechanism where user-supplied parameters are directly incorporated into output without appropriate filtering or encoding measures.
The technical implementation of this vulnerability aligns with CWE-79, which describes improper neutralization of input during web output, specifically categorizing it as a reflected cross-site scripting flaw. The vulnerability operates through the standard XSS attack vector where an attacker crafts a malicious URL containing script payloads within the tab parameter. When an authenticated user navigates to this crafted URL, the malicious script executes in their browser context, potentially leading to session hijacking, credential theft, or unauthorized actions within the WordPress administration interface. The reflected nature of this vulnerability means that the malicious payload is not stored on the server but is instead reflected back to the user through the application's response, making it particularly dangerous in targeted attack scenarios.
The operational impact of this vulnerability extends beyond simple script execution as it can enable sophisticated attack chains within WordPress environments. An attacker could leverage this vulnerability to escalate privileges, modify plugin settings, or gain unauthorized access to sensitive administrative functions. The reflected XSS nature makes this attack particularly effective when delivered through phishing campaigns or social engineering tactics, as users may unknowingly click malicious links that appear legitimate. The vulnerability affects the entire WordPress ecosystem where the plugin is installed, potentially compromising multiple sites if administrators do not update to the patched version. This type of vulnerability is particularly concerning in enterprise environments where WordPress plugins are widely deployed and may be used by multiple administrators with varying security awareness levels.
Mitigation strategies for CVE-2021-24286 require immediate action from WordPress administrators to upgrade to version 1.3.1 or later of the Redirect 404 to parent plugin. The patch addresses the core issue by implementing proper sanitization of the tab parameter before outputting it back to users, ensuring that any potentially malicious input is neutralized through appropriate encoding or filtering mechanisms. Additionally, administrators should implement comprehensive input validation practices across all plugin and theme components, following security guidelines such as those outlined in the OWASP Top Ten project. Network-level protections including web application firewalls and content security policies can provide additional defense-in-depth measures, though these should not replace proper code-level fixes. Regular security audits of WordPress installations, including plugin and theme vulnerability scanning, are essential for maintaining security posture. The ATT&CK framework categorizes this vulnerability under the T1059.007 technique for scripting, as it enables attackers to execute malicious scripts through web-based interfaces, highlighting the importance of proper input sanitization and output encoding in web application security.