CVE-2025-66103 in WPCal.io Plugin
Summary
by MITRE • 12/30/2025
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Revmakx WPCal.Io allows DOM-Based XSS.This issue affects WPCal.Io: from n/a through 0.9.5.9.
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Analysis
by VulDB Data Team • 12/30/2025
The vulnerability identified as CVE-2025-66103 represents a critical cross-site scripting weakness in the Revmakx WPCal.Io web calendar application, specifically manifesting as a DOM-based XSS flaw that enables attackers to inject malicious scripts into web pages viewed by users. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is classified as a fundamental web application security weakness that allows attackers to execute scripts in the context of other users' browsers. The issue is particularly concerning because it operates at the DOM level rather than traditional input/output validation, making it more sophisticated and potentially harder to detect through conventional security measures. The affected version range spans from an unspecified initial version through 0.9.5.9, indicating that multiple iterations of the application were susceptible to this particular weakness.
The technical flaw stems from inadequate input sanitization and improper handling of user-supplied data within the web page generation process of WPCal.Io. When users interact with the calendar application, particularly through dynamic content loading or parameter processing, the application fails to properly neutralize or escape user-provided input before incorporating it into the Document Object Model. This allows an attacker to craft malicious payloads that, when executed, can manipulate the DOM structure and execute unauthorized scripts. The DOM-based nature of this vulnerability means that the malicious code is injected directly into the page's JavaScript execution environment rather than being stored on the server, making it particularly dangerous for session hijacking, credential theft, and other client-side attacks. The vulnerability can be exploited through various attack vectors including URL parameters, form inputs, or even through manipulation of the application's JavaScript behavior.
The operational impact of this vulnerability extends beyond simple script execution, creating significant risks for both end users and system administrators. Attackers can leverage this weakness to steal user sessions, capture sensitive information, redirect users to malicious websites, or even perform actions on behalf of authenticated users. The vulnerability's presence in multiple versions suggests a persistent design flaw that was not adequately addressed during the application's development lifecycle, potentially exposing organizations using WPCal.Io to prolonged security risks. This type of vulnerability can be particularly devastating in enterprise environments where calendar applications often contain sensitive scheduling information, personal data, and business-critical meeting details. The attack surface is further expanded by the fact that DOM-based XSS vulnerabilities can be triggered through social engineering campaigns, making them more accessible to attackers with varying skill levels.
Mitigation strategies for CVE-2025-66103 should focus on comprehensive input validation and output encoding practices that align with established security frameworks. Organizations should immediately upgrade to the latest version of WPCal.Io where this vulnerability has been addressed, as the vendor has likely implemented proper sanitization of user inputs and enhanced DOM manipulation controls. The recommended approach includes implementing Content Security Policy headers to restrict script execution, utilizing proper HTML encoding for all dynamic content, and employing secure coding practices that prevent direct injection of user data into JavaScript contexts. Security teams should also consider implementing web application firewalls that can detect and block suspicious input patterns, while monitoring network traffic for potential exploitation attempts. This vulnerability aligns with ATT&CK technique T1059.007 for JavaScript execution and T1531 for credential access, making it a significant concern for threat actors seeking to establish persistent access or extract sensitive information from affected systems. The remediation process should include thorough code reviews focusing on DOM manipulation functions, input validation routines, and all dynamic content generation pathways within the application.