CVE-2026-66646 in WP Tab Widget Plugin
Summary
by MITRE • 08/18/2026
Contributor Cross Site Scripting (XSS) in WP Tab Widget <= 1.2.11 versions.
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Analysis
by VulDB Data Team • 08/18/2026
The vulnerability identified as Contributor Cross-Site Scripting within the WP Tab Widget plugin, affecting versions up to and including 1.2.11, represents a significant security flaw rooted in insufficient input validation and output encoding mechanisms. This specific weakness allows an attacker with contributor-level or lower privileges on a WordPress installation to inject malicious client-side scripts into web pages viewed by other users. The core technical issue lies in the plugin's failure to properly sanitize user-supplied data before it is rendered within tab content structures, which are frequently displayed prominently on website frontends and dashboards. By leveraging this flaw, an attacker can execute arbitrary JavaScript code in the context of a victim’s browser session, thereby bypassing standard security controls such as the Same-Origin Policy that normally restrict how documents or scripts loaded from one origin interact with resources from another.
From a technical perspective, this vulnerability is classified under Common Weakness Enumeration (CWE) ID 79, known as Improper Neutralization of Input During Web Page Generation, commonly referred to as Cross-Site Scripting. The attack vector typically involves the attacker creating or editing content within the WordPress environment that includes script tags or event handlers embedded in attributes such as onmouseover or onclick. Because the plugin does not adequately escape special characters like less-than signs, greater-than signs, and quotes before rendering them into HTML output, these scripts are executed by the victim's browser when they view the compromised tab widget content. This execution occurs within the security context of the targeted website, granting the attacker a level of trust that would otherwise be denied to external sources.
The operational impact of this vulnerability is substantial, particularly because it requires only contributor-level access rather than administrator privileges. In many WordPress installations, contributors are trusted users who may have legitimate reasons for posting content but should not possess administrative capabilities. By exploiting this XSS flaw, an attacker can steal session cookies, which often contain authentication tokens and security keys. With these credentials in hand, the attacker can hijack active sessions of other users or even administrators if they view the malicious content, leading to full account takeover. Furthermore, the attack can be used to deface websites by altering displayed content, redirect visitors to phishing sites designed to harvest sensitive information such as login credentials or financial data, and distribute malware through drive-by downloads that exploit browser vulnerabilities triggered by the injected scripts.
This vulnerability aligns with several tactics in the MITRE ATT&CK framework for enterprise security, specifically relating to Collection via Browser Redirects and Credential Access through Steal Web Session Cookie techniques. The ability of a low-privileged user to escalate their influence over the application’s output demonstrates a failure in privilege separation and input validation protocols. Such scenarios are particularly dangerous because they can be triggered by social engineering tactics where an attacker convinces a contributor or editor to publish malicious content, effectively turning legitimate users into unwitting vectors for attack without requiring direct exploitation of server-side software vulnerabilities.
Mitigation strategies must focus on immediate remediation through version updates and enhanced security configurations. The primary solution is to upgrade the WP Tab Widget plugin to a version greater than 1.2.11 where this issue has been patched by implementing proper output encoding functions such as esc_html or wp_kses_post in PHP code, ensuring that all user inputs are treated as data rather than executable code. In environments where immediate patching is not feasible due to compatibility concerns with other plugins, administrators should consider disabling the plugin entirely until a secure version can be deployed. Additionally, implementing Content Security Policy headers at the web server level can significantly mitigate the impact of any remaining XSS vulnerabilities by restricting the sources from which scripts are allowed to load and execute. Regular security audits and code reviews focusing on input validation practices across all active plugins are essential for maintaining a robust defense posture against client-side attacks in WordPress ecosystems.