CVE-2021-24992 in Smart Floating & Sticky Buttons Plugin
Summary
by MITRE • 12/27/2021
The Smart Floating / Sticky Buttons WordPress plugin before 2.5.5 does not sanitise and escape some parameter before outputting them in attributes and page, which could allow high privilege users to perform Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed.
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Analysis
by VulDB Data Team • 12/31/2021
The vulnerability identified as CVE-2021-24992 affects the Smart Floating / Sticky Buttons WordPress plugin version 2.5.4 and earlier, representing a critical cross-site scripting flaw that undermines web application security. This issue specifically targets the plugin's handling of user-supplied parameters within HTML attributes and page output, creating a pathway for malicious code execution. The vulnerability exists because the plugin fails to properly sanitise and escape input data before incorporating it into web page elements, which directly violates fundamental web security principles and industry standards.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within the plugin's codebase. When high-privilege users interact with the plugin's administrative interface, they can inject malicious script code through parameters that are not properly sanitised before being rendered in HTML attributes or page content. This flaw allows attackers with elevated privileges to execute arbitrary JavaScript code within the context of other users' browsers, potentially leading to session hijacking, data theft, or further privilege escalation. The vulnerability is particularly concerning because it can be exploited even when the WordPress installation has restricted the unfiltered_html capability, which typically prevents users from injecting raw HTML content. This demonstrates a failure in the plugin's security architecture and highlights the importance of proper input sanitisation at multiple layers of application processing.
The operational impact of CVE-2021-24992 extends beyond simple script execution, as it can enable attackers to perform sophisticated attacks that leverage the elevated privileges of compromised administrators. This includes potential data exfiltration, modification of critical plugin settings, or establishment of persistent backdoors within the WordPress environment. The vulnerability directly maps to CWE-79 which describes Cross-Site Scripting flaws, and aligns with ATT&CK technique T1566 related to spearphishing attachments and links. Organizations running affected versions of the plugin face significant risk of compromise, particularly in environments where administrative credentials are valuable targets. The vulnerability affects the plugin's core functionality by compromising the integrity of user input handling, potentially leading to unauthorized access to sensitive administrative features.
Mitigation strategies for this vulnerability require immediate action including updating to plugin version 2.5.5 or later, which contains the necessary sanitisation and escaping mechanisms. Security administrators should also implement additional protective measures such as monitoring for suspicious parameter usage within the plugin's administrative interface and reviewing user permissions to limit the number of high-privilege accounts. The WordPress security team recommends verifying the integrity of plugin installations through checksum verification and implementing web application firewalls to detect and block malicious script injection attempts. Organizations should conduct thorough vulnerability assessments of their WordPress environments to identify any other plugins with similar sanitisation issues, as this vulnerability demonstrates the importance of proper input validation across all web application components. Regular security audits and adherence to secure coding practices including input sanitisation, output encoding, and privilege separation will help prevent similar vulnerabilities from emerging in future plugin developments.