CVE-2024-0509 in WP 404 Auto Redirect to Similar Post Plugin
Summary
by MITRE • 02/06/2024
The WP 404 Auto Redirect to Similar Post plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the ‘request’ parameter in all versions up to, and including, 1.0.3 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link.
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Analysis
by VulDB Data Team • 04/11/2026
The WP 404 Auto Redirect to Similar Post plugin for WordPress presents a significant security weakness that falls under the category of reflected cross-site scripting vulnerabilities. This vulnerability affects all versions up to and including 1.0.3, creating an exploitable condition where malicious actors can inject arbitrary web scripts into the plugin's functionality. The issue stems from inadequate input sanitization and insufficient output escaping mechanisms within the plugin's codebase, specifically targeting the 'request' parameter that processes user input. The vulnerability operates by allowing attackers to craft malicious payloads that get reflected back to users through the plugin's response handling, making it particularly dangerous in environments where users interact with plugin-generated content.
The technical flaw manifests when the plugin fails to properly validate or sanitize the 'request' parameter before incorporating it into the HTTP response. This parameter typically handles user queries or search terms that the plugin uses to redirect users to similar posts when a 404 error occurs. When an attacker crafts a malicious input containing script tags or other executable code within the request parameter, the plugin processes this input without adequate sanitization, allowing the malicious code to be embedded directly into the page response. The lack of proper output escaping means that even if the input were sanitized, the plugin would not properly encode the output for safe display in web browsers, creating a dual-layer vulnerability that amplifies the attack surface.
The operational impact of this vulnerability extends beyond simple script injection, as it enables attackers to perform various malicious activities through user interaction. An unauthenticated attacker can craft specially formatted URLs that, when clicked by a victim user, execute malicious scripts in the victim's browser context. This could lead to session hijacking, credential theft, defacement of content, or redirection to malicious websites. The vulnerability is particularly concerning because it does not require authentication to exploit, making it accessible to anyone who can craft and distribute malicious links. The reflected nature of the vulnerability means that the malicious payload is not stored on the server but is instead reflected back to the user's browser through the plugin's response, making it difficult to detect through traditional server-side scanning methods.
This vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in software applications, and represents a classic example of how insufficient input validation can create dangerous security exposures. The attack vector follows the patterns described in the ATT&CK framework under T1566, specifically the technique of "Phishing with Social Engineering" where attackers use malicious links to compromise user systems. The plugin's design flaw creates an environment where user trust can be exploited, as legitimate users may inadvertently encounter malicious content while browsing sites using the vulnerable plugin. Organizations using this plugin face significant risk of user compromise, particularly in environments where users may click on links without proper security awareness training.
The recommended mitigation strategies include immediate upgrading to a patched version of the plugin if available, or implementing temporary workarounds such as input filtering at the web application firewall level. Administrators should also monitor their sites for any signs of exploitation and consider implementing Content Security Policy headers to limit the execution of unauthorized scripts. Additionally, regular security audits should be conducted to identify other potentially vulnerable plugins or components within the WordPress ecosystem, as this vulnerability demonstrates the importance of proper input sanitization and output escaping practices. The incident underscores the critical need for developers to follow secure coding practices and for organizations to maintain updated security measures across all components of their web applications.