CVE-2021-24433 in Simple Sort & Search Plugin
Summary
by MITRE • 01/16/2024
The simple sort&search WordPress plugin through 0.0.3 does not make sure that the indexurl parameter of the shortcodes "category_sims", "order_sims", "orderby_sims", "period_sims", and "tag_sims" use allowed URL protocols, which can lead to stored cross-site scripting by users with a role as low as Contributor
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Analysis
by VulDB Data Team • 06/03/2025
The vulnerability identified as CVE-2021-24433 affects the simple sort&search WordPress plugin version 0.0.3 and earlier, presenting a critical security flaw that undermines the integrity of web applications. This issue specifically targets the plugin's shortcode functionality, particularly the category_sims, order_sims, orderby_sims, period_sims, and tag_sims shortcodes. The vulnerability stems from inadequate input validation and sanitization mechanisms within the plugin's codebase, creating an exploitable condition that allows malicious actors to inject malicious content through the indexurl parameter. The flaw is particularly concerning because it requires minimal user privileges to exploit, as even contributors with limited roles can potentially leverage this vulnerability to compromise the system. This represents a significant escalation of privileges issue where low-privilege users can execute malicious scripts within the context of other users' browsers.
The technical implementation of this vulnerability resides in the plugin's failure to properly validate URL protocols used in the indexurl parameter of various shortcodes. When users with contributor roles create or modify content containing these shortcodes, the plugin accepts URLs without verifying whether they use allowed protocols such as http or https. This oversight creates a stored cross-site scripting attack vector where malicious URLs can be embedded within the shortcode parameters and subsequently executed whenever the content is rendered. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in software applications, and more precisely with CWE-601, which covers URL redirection or forward attacks. The stored nature of this XSS vulnerability means that once the malicious content is injected, it persists in the database and affects all users who view the affected pages, making it particularly dangerous in multi-user environments.
The operational impact of CVE-2021-24433 extends beyond simple script execution, as it can enable attackers to perform various malicious activities within the compromised WordPress environment. Contributors can potentially redirect users to malicious websites, steal session cookies, inject malicious advertisements, or even execute more sophisticated attacks such as defacement of the website. The vulnerability creates a persistent threat vector that can be exploited across multiple sessions and user interactions, making it difficult to contain and remediate. Attackers can craft malicious URLs that redirect users to phishing sites or deliver malware payloads, while also potentially accessing sensitive information or performing unauthorized actions within the WordPress admin interface. This vulnerability directly impacts the principle of least privilege and can be exploited to escalate privileges or compromise the entire WordPress installation through user interaction with the malicious content.
Mitigation strategies for CVE-2021-24433 should focus on immediate patching and input validation improvements to prevent the exploitation of this vulnerability. The most effective approach involves updating to the latest version of the simple sort&search plugin where the vulnerability has been addressed through proper URL protocol validation. Organizations should implement comprehensive input sanitization measures that validate all URL protocols used in shortcode parameters, ensuring that only trusted protocols such as http and https are accepted. Additionally, administrators should consider implementing Content Security Policy headers to mitigate the impact of any successful XSS attempts, and conduct thorough security audits of all installed plugins to identify similar vulnerabilities. The remediation process should also include monitoring for suspicious activity and user-generated content that may contain malicious shortcodes, while implementing proper access controls to limit contributor privileges where possible. This vulnerability demonstrates the critical importance of validating all user inputs and implementing robust security measures in web applications, aligning with ATT&CK technique T1059.006 for command and scripting interpreter and T1566 for credential access through social engineering, as attackers can leverage such vulnerabilities to establish persistent access to WordPress environments.