CVE-2024-5859 is a reflected cross-site scripting vulnerability identified in the Online Booking & Scheduling Calendar plugin for WordPress by vcita, affecting all versions up to and including 4.4.2. The vulnerability stems from improper neutralization of input during web page generation, specifically insufficient sanitization and escaping of the 'd' parameter in HTTP requests. This allows unauthenticated attackers to craft malicious URLs containing JavaScript payloads that, when clicked by a victim, execute in the context of the victim's browser session. The attack vector is network-based with no privileges required, but user interaction is necessary to trigger the exploit. The vulnerability impacts confidentiality and integrity by enabling theft of session cookies, credentials, or performing unauthorized actions on behalf of users. The reflected nature means the malicious script is not stored but delivered via crafted links. The CVSS 3.1 base score is 6.1, indicating medium severity, with a scope change due to potential impact on user sessions. No public exploits have been reported yet, but the widespread use of WordPress and this plugin increases potential exposure. The vulnerability highlights the importance of proper input validation and output encoding in web applications, especially plugins handling user input in dynamic content generation.

The primary impact of CVE-2024-5859 is the compromise of user confidentiality and integrity through reflected XSS attacks. Attackers can steal session cookies, enabling account takeover or impersonation of legitimate users. They may also perform unauthorized actions on behalf of users, such as changing booking details or accessing sensitive information. While availability is not directly affected, the loss of trust and potential data breaches can have significant reputational and operational consequences for organizations relying on the vcita plugin. Given the plugin’s role in online booking and scheduling, exploitation could disrupt business operations, lead to fraud, or expose personal customer data. The vulnerability’s ease of exploitation (no authentication required) and network accessibility increase risk, especially for organizations with public-facing WordPress sites using this plugin. The lack of known exploits in the wild currently reduces immediate threat but does not eliminate future risk. Organizations globally that use this plugin are at risk, particularly those with high volumes of customer interactions via WordPress-based booking systems.

1. Upgrade the Online Booking & Scheduling Calendar plugin to a version that patches this vulnerability once available from vcita. Monitor vendor announcements closely. 2. Until a patch is released, implement Web Application Firewall (WAF) rules to detect and block malicious payloads targeting the 'd' parameter, focusing on typical XSS attack patterns. 3. Enforce strict Content Security Policy (CSP) headers to restrict execution of inline scripts and untrusted sources, mitigating impact of reflected XSS. 4. Sanitize and validate all user inputs on the server side, especially parameters used in dynamic page generation, to prevent injection of malicious code. 5. Educate users and administrators about phishing risks and the dangers of clicking suspicious links, as user interaction is required for exploitation. 6. Conduct regular security audits and penetration testing on WordPress sites using this plugin to identify and remediate injection flaws. 7. Consider disabling or limiting the use of the affected plugin if immediate patching is not feasible, especially on high-risk or sensitive sites. 8. Monitor logs for unusual requests targeting the 'd' parameter or other suspicious activity indicative of attempted exploitation.