CVE-2024-9599 in Popup Box Plugin
Summary
by MITRE • 05/16/2025
The Popup Box WordPress plugin before 4.7.8 does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).
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Analysis
by VulDB Data Team • 06/05/2025
The Popup Box WordPress plugin version 4.7.8 and earlier contains a critical stored cross-site scripting vulnerability that affects high-privilege users including administrators. This vulnerability stems from inadequate input sanitization and output escaping mechanisms within the plugin's settings handling functionality. The flaw specifically impacts environments where the unfiltered_html capability has been restricted, such as multisite WordPress installations where security hardening is typically enforced. Attackers with administrator privileges can exploit this weakness to inject malicious scripts into the plugin's configuration settings, which then get executed whenever the affected settings are rendered in the WordPress admin interface.
The technical implementation of this vulnerability resides in the plugin's failure to properly sanitize user-supplied input before storing it in the database and subsequently outputting it without adequate escaping. This represents a classic stored XSS flaw that aligns with CWE-79, which defines the vulnerability as the insertion of malicious code into web applications where the code is then stored and executed by other users. The vulnerability is particularly concerning because it operates within the WordPress admin context, where administrators typically have elevated privileges and access to sensitive system functions. The flaw essentially allows an attacker to bypass standard security measures that would normally prevent script execution in admin areas.
From an operational perspective, this vulnerability creates significant risk for WordPress multisite environments where security policies are strictly enforced. The restriction of unfiltered_html capability is a common security practice designed to prevent arbitrary HTML injection, yet this vulnerability demonstrates how insufficient sanitization in plugin components can undermine such protections. The attack vector requires an attacker to already possess administrator-level access, but the impact is substantial as it can lead to complete compromise of the WordPress administration interface. Once exploited, the malicious scripts could potentially steal session cookies, modify plugin settings, or redirect administrators to malicious sites, effectively allowing persistent access to the compromised WordPress installation.
The implications of this vulnerability extend beyond immediate script execution as it represents a broader class of issues in WordPress plugin development where third-party components fail to adhere to proper security coding practices. The vulnerability demonstrates the importance of implementing comprehensive input validation and output escaping mechanisms, particularly in admin-facing interfaces where privileged users interact with plugin settings. Organizations should consider the ATT&CK framework's technique T1547.001, which addresses the exploitation of administrative privileges through malicious code injection, as this vulnerability essentially provides a pathway for attackers to leverage existing administrative access for more extensive compromise. Mitigation strategies should include immediate plugin updates to version 4.7.8 or later, along with comprehensive monitoring for any suspicious administrative activities and regular security audits of plugin configurations.