CVE-2016-20084 in Booking Calendar Contact Plugin
Summary
by MITRE • 06/15/2026
WordPress appointment-booking-calendar 1.1.24 contains multiple privilege escalation vulnerabilities that allow unauthenticated attackers to modify calendar settings and inject persistent cross-site scripting payloads through the admin.php page parameters. Attackers can inject malicious JavaScript into the 'ict' and 'ics' options or the calendar 'name' parameter via GET requests to execute arbitrary scripts when the calendar is displayed or accessed in the administration interface.
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Analysis
by VulDB Data Team • 06/15/2026
This vulnerability in WordPress appointment-booking-calendar version 1.1.24 represents a critical privilege escalation flaw that undermines the security model of the plugin. The vulnerability stems from insufficient input validation and sanitization mechanisms within the admin.php page parameters, allowing unauthenticated attackers to manipulate administrative functions without proper authentication. The flaw specifically affects the 'ict' and 'ics' options and the calendar 'name' parameter, which are processed through GET requests, creating a direct pathway for malicious input injection. This vulnerability aligns with CWE-20, representing improper input validation, and CWE-79, indicating cross-site scripting vulnerabilities, as the system fails to properly sanitize user-supplied data before processing or rendering it within the administrative interface. The attack vector operates through the exploitation of weak access controls and inadequate parameter validation, enabling attackers to bypass normal authentication mechanisms and assume elevated privileges within the calendar management system.
The operational impact of this vulnerability extends beyond simple data manipulation to encompass full administrative control over the calendar plugin functionality. Attackers can modify calendar settings, alter booking configurations, and inject persistent cross-site scripting payloads that remain active until manually removed. The malicious JavaScript injection occurs when the calendar is displayed or accessed through the administration interface, creating a persistent threat that affects all users who view the compromised calendar data. This vulnerability enables attackers to execute arbitrary scripts in the context of the victim's browser, potentially leading to session hijacking, data exfiltration, or further exploitation of the WordPress installation. The persistence of these XSS payloads means that every subsequent access to the affected calendar page could serve the malicious code to users, creating an ongoing security risk that compounds over time. The vulnerability affects not just the calendar plugin itself but potentially the entire WordPress installation, as successful exploitation could lead to further privilege escalation or lateral movement within the system.
Mitigation strategies must address both the immediate vulnerability and broader security posture of the WordPress environment. The most immediate solution involves applying the latest plugin updates from the vendor, which should include proper input sanitization and access control measures. Administrators should implement comprehensive input validation for all parameters processed through GET requests, particularly those related to administrative functions. The implementation of Content Security Policy headers can provide additional protection against XSS attacks by restricting the sources from which scripts can be executed within the browser context. Regular security audits of WordPress plugins and themes should be conducted to identify similar vulnerabilities, with particular attention to plugins handling administrative functions or user input. Network-level protections such as web application firewalls can help detect and block malicious requests attempting to exploit this vulnerability. Additionally, implementing role-based access controls and regularly reviewing user permissions can limit the potential impact of successful exploitation attempts. The vulnerability demonstrates the importance of following secure coding practices and adhering to OWASP Top Ten security guidelines, particularly regarding input validation and access control mechanisms. Organizations should also consider implementing automated vulnerability scanning tools that can detect similar issues in other plugins or custom code components within their WordPress installations.