CVE-2014-7138 in Google Calendar Events
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Google Calendar Events plugin before 2.0.4 for WordPress allows remote attackers to inject arbitrary web script or HTML via the gce_feed_ids parameter in a gce_ajax action to wp-admin/admin-ajax.php.
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Analysis
by VulDB Data Team • 12/13/2024
The vulnerability described in CVE-2014-7138 represents a critical cross-site scripting flaw within the Google Calendar Events plugin for WordPress, specifically affecting versions prior to 2.0.4. This vulnerability resides in the plugin's handling of user-supplied input through the gce_feed_ids parameter within the gce_ajax action that processes requests through wp-admin/admin-ajax.php. The flaw enables remote attackers to execute malicious web scripts or HTML code in the context of affected websites, potentially compromising user sessions and data integrity. The vulnerability operates by failing to properly sanitize or escape user input before incorporating it into dynamic web content, creating an avenue for attackers to inject malicious payloads that execute in the browsers of unsuspecting users.
The technical implementation of this XSS vulnerability stems from insufficient input validation and output sanitization within the plugin's ajax handling mechanism. When the gce_ajax action processes requests containing the gce_feed_ids parameter, the plugin fails to adequately filter or escape the input before rendering it within the web page context. This improper handling allows attackers to inject malicious scripts that can execute in the browser context of authenticated users who view affected calendar feeds or pages. The vulnerability specifically targets the wp-admin/admin-ajax.php endpoint which serves as a central point for handling asynchronous requests in WordPress, making it a prime target for exploitation. The flaw falls under CWE-79 - Improper Neutralization of Input During Web Page Generation, which is a fundamental weakness in web application security where user-controllable data is not properly sanitized before being rendered in web pages.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable sophisticated attacks including session hijacking, credential theft, and data exfiltration. Attackers can craft malicious payloads that redirect users to phishing sites, steal cookies and session tokens, or even modify calendar events to propagate further attacks. The vulnerability particularly affects WordPress administrators and users who have access to calendar feeds, as these individuals are most likely to encounter the malicious content. Given that Google Calendar Events plugin was widely used, the potential attack surface was substantial, with numerous WordPress installations vulnerable to this flaw. The attack requires minimal privileges as it operates over standard web protocols and does not require authentication to the target system. This vulnerability aligns with ATT&CK technique T1566.001 - Phishing: Spearphishing Attachment, as it can be delivered through malicious calendar feeds that users might legitimately access, and T1566.002 - Phishing: Spearphishing Link, when attackers craft malicious URLs that exploit this vulnerability.
Mitigation strategies for this vulnerability involve immediate patching of the affected plugin to version 2.0.4 or later, which implements proper input sanitization and output escaping mechanisms. System administrators should also implement Content Security Policy headers to limit the sources from which scripts can be executed on calendar pages, providing an additional layer of protection against XSS attacks. Input validation should be strengthened at multiple levels including server-side validation of all parameters passed to the gce_ajax endpoint, and output escaping should be enforced when rendering calendar data. Organizations should also consider implementing web application firewalls that can detect and block suspicious patterns in requests targeting the wp-admin/admin-ajax.php endpoint. Regular security audits of WordPress plugins and themes should be conducted to identify similar vulnerabilities, and automated patch management systems should be deployed to ensure timely updates. The vulnerability serves as a reminder of the importance of proper input validation and output sanitization in web applications, particularly those handling user-generated content or data from external sources.