CVE-2021-24567 in Simple Post Plugin
Summary
by MITRE • 01/16/2024
The Simple Post WordPress plugin through 1.1 does not sanitize user input when an authenticated user Text value, then it does not escape these values when outputting to the browser leading to an Authenticated Stored XSS Cross-Site Scripting issue.
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Analysis
by VulDB Data Team • 04/20/2025
The Simple Post WordPress plugin version 1.1 contains a critical security vulnerability classified as an authenticated stored cross-site scripting flaw that affects users with sufficient privileges to create or modify posts. This vulnerability arises from inadequate input sanitization and output escaping mechanisms within the plugin's codebase, creating a persistent security risk that can be exploited by authenticated attackers who possess basic user permissions. The flaw specifically manifests when the plugin processes text input values from authenticated users without proper sanitization before storing them in the database, and subsequently fails to escape these stored values when rendering them back to the browser for display. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, representing a fundamental weakness in input validation and output encoding practices that has been consistently identified as one of the most prevalent web application security flaws by the Open Web Application Security Project.
The operational impact of this vulnerability extends beyond simple script execution within the browser context, as it allows authenticated attackers to inject malicious scripts that can persistently affect other users who view the affected content. When an attacker with appropriate privileges creates or modifies a post containing malicious script code, the script is stored in the WordPress database and subsequently executed whenever other users view the content, potentially enabling session hijacking, credential theft, or redirection to malicious websites. The stored nature of this XSS vulnerability means that the malicious payload remains active until manually removed from the database, creating a persistent threat vector that can affect multiple users over extended periods. This particular vulnerability aligns with ATT&CK technique T1531 which focuses on the use of malicious scripts to gain unauthorized access and maintain persistence within web applications, making it particularly dangerous in environments where multiple users interact with the same content management system.
Mitigation strategies for this vulnerability should prioritize immediate plugin updates to versions that address the sanitization and escaping issues, as the original vulnerable version 1.1 represents an outdated release that lacks proper security controls. System administrators should implement comprehensive input validation measures that sanitize all user-provided content before storage, ensuring that any potentially malicious script tags or executable code are properly escaped or removed. Additionally, organizations should consider implementing Content Security Policy headers to limit the execution of inline scripts and restrict the sources from which scripts can be loaded, providing an additional layer of protection against XSS attacks. Regular security audits and vulnerability assessments should be conducted to identify similar issues in other plugins and themes, as this vulnerability demonstrates the importance of proper input handling and output encoding practices throughout the entire web application stack. The remediation process should also include monitoring for any unauthorized modifications to content and implementing proper access controls to limit the ability of low-privilege users to inject malicious content into the system.