CVE-2024-13410 is a high-severity vulnerability classified under CWE-502 (Deserialization of Untrusted Data) found in the CozyStay and TinySalt WordPress plugins developed by LoftOcean. Both plugins, up to versions 1.7.0 and 3.9.0 respectively, improperly handle deserialization in the 'ajax_handler' function, accepting untrusted input that can be manipulated by unauthenticated attackers to inject PHP objects. This PHP Object Injection vulnerability enables attackers to exploit the deserialization process to execute arbitrary code or perform other malicious actions. However, the vulnerability alone does not guarantee exploitation; it requires the presence of a gadget chain (POP chain) in other installed plugins or themes to achieve meaningful impact. Such gadget chains enable attackers to leverage the injected objects to perform actions like deleting arbitrary files, accessing sensitive information, or executing arbitrary code on the server. The vulnerability is remotely exploitable without any authentication or user interaction, making it highly dangerous. Despite the lack of known public exploits at the time of disclosure, the CVSS 3.1 base score of 9.8 indicates critical severity due to the potential for complete system compromise. The flaw affects all versions of the CozyStay and TinySalt plugins up to the specified versions, which are commonly used in WordPress hotel booking websites. No official patches were linked at the time of disclosure, so mitigation may require manual intervention or plugin updates once available.

If exploited, this vulnerability could lead to full compromise of affected WordPress sites running CozyStay or TinySalt plugins. Attackers could execute arbitrary code remotely, delete or modify files, and access sensitive data stored on the server. This can result in website defacement, data breaches, service disruption, and potentially pivoting to other internal systems. Given that WordPress powers a significant portion of websites globally, including many small to medium businesses in the hospitality sector using these themes/plugins, the impact can be widespread. The unauthenticated nature of the exploit increases the risk of automated attacks and mass exploitation attempts. Organizations relying on these plugins for booking or customer data management face risks to confidentiality, integrity, and availability of their systems and data. The absence of a known exploit in the wild currently reduces immediate risk but does not diminish the urgency to address the vulnerability before attackers develop weaponized exploits.

1. Immediately update CozyStay and TinySalt plugins to the latest versions once patches are released by LoftOcean. 2. In the absence of official patches, disable or remove the vulnerable plugins to eliminate the attack surface. 3. Conduct an inventory of all installed WordPress plugins and themes to identify potential POP chains that could be leveraged in conjunction with this vulnerability; remove or update those components accordingly. 4. Implement Web Application Firewall (WAF) rules to detect and block suspicious deserialization payloads targeting the 'ajax_handler' endpoint. 5. Restrict access to the WordPress admin-ajax.php endpoint by IP or authentication where feasible to reduce exposure. 6. Monitor logs for unusual POST requests or attempts to inject serialized PHP objects. 7. Employ least privilege principles for WordPress file permissions and server user accounts to limit damage scope if exploited. 8. Regularly back up website data and configurations to enable recovery in case of compromise. 9. Educate site administrators about the risks of installing untrusted plugins and the importance of timely updates. 10. Consider using security plugins that detect and prevent PHP object injection and deserialization attacks.