CVE-2024-8663 is a reflected Cross-Site Scripting (XSS) vulnerability identified in the WP Simple Booking Calendar plugin for WordPress, a popular tool for managing booking calendars on websites. The vulnerability stems from the plugin's use of WordPress functions add_query_arg and remove_query_arg without proper escaping of URL parameters. These functions manipulate query strings but, when used improperly, can allow injection of malicious JavaScript code into URLs. Since the plugin fails to sanitize or encode these inputs correctly, an attacker can craft a malicious URL containing script code. When a victim clicks this URL, the injected script executes in their browser context, potentially stealing cookies, session tokens, or performing actions on behalf of the user. The vulnerability affects all versions up to and including 2.0.10. It requires no authentication but does require user interaction (clicking a malicious link). The CVSS 3.1 score of 6.1 reflects a medium severity, with network attack vector, low attack complexity, no privileges required, but user interaction necessary. The vulnerability impacts 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 is categorized under CWE-79, which covers improper neutralization of input during web page generation leading to XSS. This vulnerability could be leveraged in phishing campaigns or to escalate attacks on site visitors or administrators.

The primary impact of CVE-2024-8663 is the compromise of user confidentiality and integrity on websites using the WP Simple Booking Calendar plugin. Attackers can execute arbitrary scripts in the context of the victim's browser, potentially stealing session cookies, credentials, or performing unauthorized actions on behalf of the user. This can lead to account takeover, data theft, or further exploitation of the affected website. Since the vulnerability is reflected XSS, it requires social engineering to lure victims into clicking malicious links, making it a vector for phishing attacks. Organizations relying on this plugin for booking or reservation services risk reputational damage, loss of customer trust, and potential regulatory consequences if user data is compromised. The vulnerability does not directly affect system availability but can be a stepping stone for more complex attacks. The lack of authentication requirement broadens the attacker base, and the widespread use of WordPress and booking plugins increases the potential attack surface globally.

1. Immediate mitigation involves updating the WP Simple Booking Calendar plugin to a version where this vulnerability is fixed; if no patch is available, consider disabling the plugin temporarily. 2. Implement Web Application Firewall (WAF) rules to detect and block malicious query strings targeting the vulnerable parameters. 3. Employ Content Security Policy (CSP) headers to restrict execution of unauthorized scripts on affected pages. 4. Sanitize and encode all user inputs and URL parameters rigorously, especially those manipulated by add_query_arg and remove_query_arg functions. 5. Educate users and administrators about phishing risks and encourage caution when clicking on unexpected links. 6. Monitor web server logs for suspicious URL patterns that may indicate exploitation attempts. 7. Consider isolating booking calendar functionality or using alternative plugins with better security track records until a fix is available. 8. Conduct regular security assessments and penetration testing focused on XSS vulnerabilities in web applications.