CVE-2026-110903 in The Events Calendar Plugin
Summary
by MITRE • 10/16/2026
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Liquid Web / StellarWP The Events Calendar the-events-calendar allows Stored XSS.This issue affects The Events Calendar: from n/a through 6.18.1.
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Analysis
by VulDB Data Team • 10/16/2026
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 manifests as a Stored XSS within the The Events Calendar plugin for WordPress, developed by StellarWP and distributed through Liquid Web infrastructure. Unlike reflected XSS attacks where malicious scripts are executed immediately via a crafted URL, stored vulnerabilities persist on the target server's database. This means that once an attacker successfully injects malicious code into a data field such as event descriptions, titles, or organizer information, the payload is saved permanently until manually removed by an administrator. Consequently, every user who views the affected page will have their browser execute the injected script in the context of the vulnerable website, significantly amplifying the potential impact and scope of the compromise compared to transient attack vectors.
The technical root cause lies in insufficient input validation or output encoding mechanisms within versions 6.18.1 and earlier of The Events Calendar. When user-supplied data is processed for storage without proper sanitization, special characters that hold semantic meaning in HTML and JavaScript are not escaped correctly. This allows an attacker to inject executable script tags, event handlers, or other malicious payloads directly into the database entries associated with calendar events. Because WordPress themes often render these stored values dynamically within web pages, the browser interprets the injected code as legitimate content belonging to the site domain. This bypasses same-origin policy protections, allowing the malicious scripts to access cookies, session tokens, local storage, and other sensitive data tied to the user's current authentication state with The Events Calendar or any integrated WordPress services.
From an operational perspective, this vulnerability poses a severe risk to both website administrators and end-users. An attacker can exploit this flaw to hijack administrative sessions by stealing cookie-based authentication credentials, potentially leading to full control over the WordPress installation. Beyond session hijacking, the stored nature of the XSS allows for persistent defacement of the calendar interface or redirection of users to phishing sites designed to steal further credentials. In enterprise environments where The Events Calendar is used for scheduling sensitive meetings or public events, this could also facilitate drive-by downloads if combined with other vulnerabilities in browser plugins or extensions. The persistence of the payload means that even after the initial discovery and patching of the vulnerability, existing malicious entries may continue to affect users until they are explicitly cleaned from the database, creating a prolonged window of exposure for organizations relying on timely maintenance cycles.
To mitigate this risk, immediate action is required by upgrading The Events Calendar to version 6.18.2 or later, where these input handling mechanisms have been corrected. Administrators should also audit existing event entries for any suspicious script tags or encoded payloads that may have been injected prior to the patch application. Implementing a Web Application Firewall can provide an additional layer of defense by filtering out common XSS patterns in HTTP requests before they reach the application logic. Furthermore, adopting strict Content Security Policy headers can help mitigate the impact of successful exploits by restricting the sources from which scripts are allowed to load and execute. Regular security audits and adherence to secure coding standards such as OWASP Top Ten guidelines will ensure that future developments incorporate robust input validation and output encoding practices to prevent similar vulnerabilities from arising in other components of the web application stack.