CVE-2026-66645 in Table Of Contents Block Plugin
Summary
by MITRE • 08/18/2026
Contributor Cross Site Scripting (XSS) in Table Of Contents Block <= 1.5.0 versions.
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Analysis
by VulDB Data Team • 08/18/2026
The vulnerability identified as Contributor Cross-Site Scripting within the Table of Contents block for WordPress plugin versions up to 1.5.0 represents a significant security risk associated with insufficient input validation and output encoding mechanisms. This specific flaw allows authenticated users, particularly those holding contributor-level privileges or lower, to inject malicious client-side scripts into web pages viewed by other users. The root cause lies in the application's failure to properly sanitize user-supplied data before it is rendered within the table of contents structure. When a user inputs text that contains executable JavaScript code through the plugin’s interface, the system processes this input without applying adequate encoding or filtering rules designed to neutralize script tags and event handlers. Consequently, when another user accesses a page containing the affected content, their browser executes the injected scripts in the context of the vulnerable site, leading to a classic stored cross-site scripting scenario where the malicious payload persists on the server until manually removed.
From an operational perspective, this vulnerability enables attackers to perform actions that compromise the confidentiality, integrity, and availability of user data and application functionality. An attacker can steal session cookies or authentication tokens, effectively hijacking user sessions and gaining unauthorized access to administrative accounts if they manage to capture credentials from privileged users. Furthermore, the ability to execute arbitrary JavaScript allows for defacement of web pages, redirection of victims to malicious sites hosting malware or phishing content, and manipulation of DOM elements to deceive users into performing unintended actions such as transferring funds or changing account settings. The impact is particularly severe because it exploits a feature commonly used by contributors who may not have full administrative oversight but still possess the ability to publish content that affects all site visitors, thereby widening the attack surface significantly beyond just administrator accounts.
This vulnerability aligns with CWE-79, which classifies Improper Neutralization of Input During Web Page Generation known as Cross-site Scripting (XSS). The specific mechanism involves stored XSS where malicious scripts are permanently stored on target servers and subsequently retrieved when users request legitimate data. In terms of the MITRE ATT&CK framework, this activity maps to techniques under T1059 Command and Control scripting such as JavaScript execution within a browser environment, facilitating lateral movement or further exploitation depending on the context of the web application. The lack of proper output encoding means that special characters like angle brackets are not converted into their HTML entity equivalents, allowing the browser interpreter to parse them as code rather than plain text data.
Mitigation strategies must focus on implementing robust input validation and strict output encoding practices within the plugin’s development lifecycle. Developers should ensure that all user inputs are validated against a whitelist of allowed characters before processing and apply context-aware output encoding when rendering data in HTML, JavaScript, or CSS contexts. Utilizing established security libraries for escaping special characters is essential to prevent script injection. Additionally, implementing Content Security Policy headers can provide an additional layer of defense by restricting the sources from which scripts are loaded and executed, thereby mitigating the impact even if a vulnerability exists. For immediate remediation, users should update the Table Of Contents plugin to version 1.5.1 or later where this issue has been addressed through enhanced sanitization routines. Until updates are applied, administrators can consider restricting contributor-level access to content that generates dynamic table of contents entries or manually reviewing and cleaning user-generated content for malicious scripts as a temporary countermeasure.