CVE-2024-8549 is a reflected Cross-Site Scripting (XSS) vulnerability identified in the Simple Calendar – Google Calendar Plugin for WordPress, which is widely used to embed Google Calendar data into WordPress sites. The vulnerability stems from the plugin's use of the WordPress function add_query_arg without proper escaping or sanitization of user-supplied input in URL parameters. This improper neutralization of input (classified under CWE-79) allows attackers to craft malicious URLs containing executable JavaScript code. When a victim clicks such a link, the injected script executes in the context of the vulnerable website, potentially allowing theft of cookies, session tokens, or other sensitive information, as well as manipulation of the webpage content. The vulnerability affects all versions up to and including 3.4.2. Exploitation requires no authentication but does require user interaction (clicking a malicious link). The CVSS 3.1 base score is 6.1, indicating a medium severity level, with attack vector network, low attack complexity, no privileges required, user interaction required, and impacts on confidentiality and integrity but not availability. No patches or fixes are currently linked, and no known exploits have been reported in the wild as of the publication date. The vulnerability’s scope is limited to websites using this plugin, but given the popularity of WordPress and this plugin, the potential attack surface is significant.

The primary impact of CVE-2024-8549 is on the confidentiality and integrity of affected websites and their users. Successful exploitation can lead to theft of sensitive user data such as session cookies, enabling session hijacking, or manipulation of webpage content to perform phishing or deliver malware. This can damage the reputation of affected organizations, lead to user trust erosion, and potentially cause regulatory compliance issues if personal data is compromised. Since the vulnerability is reflected XSS, it requires user interaction, limiting automated exploitation but still posing a significant risk through social engineering. The vulnerability does not directly affect availability but could be leveraged as part of a broader attack chain. Organizations worldwide using the Simple Calendar plugin on WordPress sites are at risk, especially those with high traffic or sensitive user bases. The lack of authentication requirement increases the ease of exploitation, while the medium CVSS score reflects a moderate but actionable threat.

To mitigate CVE-2024-8549, organizations should immediately review their use of the Simple Calendar – Google Calendar Plugin and apply any available updates or patches once released by the vendor. In the absence of an official patch, administrators should consider disabling the plugin temporarily or removing it if not essential. Developers and site administrators should ensure that all URL parameters processed by add_query_arg or similar functions are properly escaped and sanitized using WordPress’s built-in escaping functions such as esc_url() or esc_html() before output. Implementing a Web Application Firewall (WAF) with rules to detect and block reflected XSS payloads targeting this plugin can provide interim protection. Educating users to avoid clicking suspicious links and employing Content Security Policy (CSP) headers can reduce the risk of script execution. Regular security audits and monitoring for unusual activity related to this plugin are also recommended. Finally, organizations should maintain an inventory of WordPress plugins to quickly identify and respond to vulnerabilities.