CVE-2021-24331 in mooth Scroll Page Buttons Plugin
Summary
by MITRE • 06/02/2021
The Smooth Scroll Page Up/Down Buttons WordPress plugin before 1.4 did not properly sanitise and validate its settings, such as psb_distance, psb_buttonsize, psb_speed, only validating them client side. This could allow high privilege users (such as admin) to set XSS payloads in them
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Analysis
by VulDB Data Team • 06/05/2021
The vulnerability identified as CVE-2021-24331 affects the Smooth Scroll Page Up/Down Buttons WordPress plugin version 1.3 and earlier, representing a critical security flaw that stems from insufficient input validation and sanitization practices. This issue specifically targets the plugin's handling of user-defined settings including psb_distance, psb_buttonsize, and psb_speed parameters. The flaw arises from the plugin's improper implementation of server-side validation mechanisms, creating an avenue for cross-site scripting attacks through the manipulation of these configurable parameters.
The technical nature of this vulnerability places it squarely within the realm of CWE-79 - Cross-Site Scripting, which occurs when an application incorporates untrusted data into web pages without proper validation or escaping. The plugin's design relied entirely on client-side validation mechanisms, a practice that fundamentally undermines security as client-side controls can be easily bypassed by attackers. This approach violates the principle of defense in depth, where security controls should operate at multiple layers to prevent exploitation. The vulnerability specifically affects high-privilege users such as administrators who possess the capability to modify plugin settings, making the attack vector particularly dangerous as it allows for privilege escalation through the manipulation of trusted administrative interfaces.
The operational impact of this vulnerability extends beyond simple script injection, as it provides attackers with the means to execute malicious code within the context of the victim's browser session. When administrators modify the plugin settings, the XSS payloads are stored and subsequently executed whenever the page is rendered, potentially leading to session hijacking, data theft, or further compromise of the WordPress installation. The vulnerability creates a persistent threat that can affect all users who view pages utilizing the affected plugin, as the stored malicious scripts execute automatically in their browsers. This makes the attack particularly insidious as it can propagate through legitimate administrative actions without requiring additional user interaction.
Mitigation strategies for CVE-2021-24331 focus primarily on immediate remediation through plugin updates to version 1.4 or later, which addresses the core validation and sanitization issues. Organizations should implement comprehensive security auditing of their WordPress installations to identify all instances of vulnerable plugins and ensure proper patch management protocols are in place. The solution involves implementing robust server-side validation that properly sanitizes all user inputs before processing, utilizing WordPress's built-in sanitization functions and escaping mechanisms. Additionally, security best practices should include restricting administrative privileges to only essential personnel, implementing content security policies, and conducting regular security assessments to identify similar vulnerabilities in other plugins or themes. This vulnerability highlights the critical importance of server-side validation as a primary defense mechanism, reinforcing the ATT&CK framework's emphasis on input validation and sanitization techniques to prevent exploitation of web application vulnerabilities.