CVE-2021-24564 in WPFront Scroll Top Plugin
Summary
by MITRE • 08/23/2021
The WPFront Scroll Top WordPress plugin before 2.0.6.07225 does not sanitise or escape its Image ALT setting before outputting it attributes, leading to an Authenticated Stored Cross-Site Scripting issues even when the unfiltered_html capability is disallowed.
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Analysis
by VulDB Data Team • 08/26/2021
The vulnerability identified as CVE-2021-24564 affects the WPFront Scroll Top WordPress plugin version 2.0.5.07225 and earlier, representing a critical authenticated stored cross-site scripting flaw that undermines web application security. This vulnerability specifically targets the plugin's handling of the Image ALT setting parameter within its user interface configuration. The flaw exists because the plugin fails to properly sanitise or escape user-provided input before incorporating it into HTML attributes during output rendering, creating a persistent XSS vector that can be exploited by authenticated users with sufficient privileges.
The technical implementation of this vulnerability stems from inadequate input validation and output escaping mechanisms within the plugin's codebase. When administrators or users with appropriate capabilities configure the plugin's Image ALT attribute, the system accepts raw user input without proper sanitisation processes. This oversight allows malicious actors to inject malicious scripts into the ALT attribute field, which then gets rendered in the HTML output without proper escaping. The vulnerability is particularly concerning because it operates even when the WordPress unfiltered_html capability is restricted, indicating that the plugin bypasses WordPress's built-in security measures designed to prevent such attacks.
From an operational perspective, this authenticated stored XSS vulnerability presents significant risks to WordPress installations using the affected plugin. An attacker with access to the WordPress admin panel or a user account with sufficient privileges can store malicious JavaScript code within the plugin's configuration settings. When other users view pages where this plugin is active, the stored script executes in their browsers, potentially leading to session hijacking, credential theft, or redirection to malicious websites. The vulnerability's persistence stems from the stored nature of the attack vector, meaning that once the malicious payload is injected, it remains active until manually removed from the plugin configuration.
The security implications of CVE-2021-24564 align with CWE-79, which categorizes cross-site scripting vulnerabilities as a fundamental web application security weakness. This classification reflects the core issue where user-supplied data is not properly escaped before being rendered in web pages. The ATT&CK framework would categorize this vulnerability under T1548.001 for privilege escalation through abuse of application permissions, as the flaw requires only authenticated access to execute malicious code. Additionally, the vulnerability demonstrates characteristics of T1211 for exploitation of web application vulnerabilities, particularly in how it leverages configuration settings to establish persistent attack vectors.
The recommended mitigation strategy involves immediately updating the WPFront Scroll Top plugin to version 2.0.6.07225 or later, which contains the necessary sanitisation fixes. Administrators should also conduct thorough security audits of all installed plugins to identify similar vulnerabilities that might exist in other third-party components. Additional protective measures include implementing strict input validation policies, regularly monitoring plugin configurations for unauthorized changes, and ensuring that user privileges are properly restricted through the principle of least privilege. Network monitoring solutions should also be configured to detect anomalous script execution patterns that might indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper input sanitisation and output escaping in web applications, particularly when dealing with user-provided content that will be rendered in HTML contexts.