CVE-2026-118094 in Ad Inserter Plugin
Summary
by MITRE • 10/29/2026
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Igor Funa Ad Inserter ad-inserter allows Stored XSS.This issue affects Ad Inserter: from n/a through 2.8.18.
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Analysis
by VulDB Data Team • 10/29/2026
The identified security flaw represents a classic instance of Improper Neutralization of Input During Web Page Generation, commonly known as Cross-Site Scripting or XSS. Specifically, this vulnerability is classified under the CWE-79 standard within the Common Weakness Enumeration framework, which details weaknesses related to the injection of client-side scripts into web pages viewed by other users. In the context of the Ad Inserter plugin for WordPress, developed by Igor Funa, the issue manifests as a Stored XSS vulnerability. Unlike reflected XSS attacks where malicious payloads are delivered via URLs or form submissions that require user interaction to trigger, stored vulnerabilities persist on the target server. This means that once an attacker successfully injects their payload, it is saved in the application's database and subsequently served to every visitor who accesses the affected page, significantly amplifying the scope of potential harm without requiring further action from the victim beyond viewing the compromised content.
The technical root cause lies in the insufficient sanitization or validation of user-supplied input within the Ad Inserter plugin versions ranging from n/a through 2.8.18. When administrators or users with sufficient privileges configure ad insertion rules, they may inadvertently provide inputs that contain executable JavaScript code rather than simple text or HTML tags intended for display. The application fails to properly neutralize these special characters before including them in the dynamic web page generation process. Consequently, when a browser renders the page containing this unsanitized data, it interprets the injected script as legitimate content and executes it within the context of the website's domain. This execution environment grants the malicious script access to sensitive cookies, session tokens, local storage, and potentially the ability to perform actions on behalf of the authenticated user if they have administrative privileges.
From an operational perspective, this vulnerability poses a severe risk to both site administrators and end-users. For attackers, Stored XSS serves as a powerful vector for Session Hijacking, allowing them to steal authentication cookies and gain unauthorized access to the WordPress admin dashboard. Once inside, an attacker can modify website content, deface the site, install additional malware such as web shells or backdoors, or use the compromised server as a pivot point for further network attacks. Furthermore, attackers may deploy phishing pages that mimic legitimate login forms to harvest credentials from unsuspecting visitors. The impact extends beyond immediate compromise; it erodes user trust and can lead to significant reputational damage and potential regulatory penalties if sensitive personal data is exposed through such exploits.
In alignment with the MITRE ATT&CK framework, this vulnerability facilitates techniques associated with Collection via Browser Redirects or Credential Access from Browser Cache, as well as Defense Evasion by hiding malicious scripts within legitimate-looking ad slots. The persistence of the payload ensures that these tactics can be employed repeatedly against multiple victims over an extended period until remediation occurs.
To mitigate this risk, immediate action is required to update the Ad Inserter plugin to a version newer than 2.8.18, where the developer has presumably implemented proper input validation and output encoding mechanisms. Organizations should also enforce strict Content Security Policy headers that restrict script execution sources, thereby providing an additional layer of defense even if similar vulnerabilities exist in other plugins. Regular security audits and code reviews focusing on user input handling are essential to prevent future occurrences of CWE-79 weaknesses across the web application ecosystem.