The Contact Form Plugin by Fluent Forms for Quiz, Survey, and Drag & Drop WP Form Builder for WordPress suffers from a PHP Object Injection vulnerability (CVE-2024-4157) due to unsafe deserialization of untrusted data in the extractDynamicValues function. This vulnerability is classified under CWE-502 (Deserialization of Untrusted Data). It affects all versions up to and including 5.1.15. An attacker with authenticated contributor-level access or higher can exploit this flaw by injecting crafted PHP objects. If a gadget chain (POP chain) is available through other installed plugins or themes, the attacker could leverage this to perform destructive actions such as arbitrary file deletion, sensitive data retrieval, or remote code execution. The attack requires the attacker to have explicit "View Form" and "Manage Form" permissions, which are set by administrators. However, this permission requirement can be bypassed if the attacker chains this vulnerability with CVE-2024-2771, increasing the risk of exploitation. The vulnerability has a CVSS v3.1 score of 7.5, reflecting high impact on confidentiality, integrity, and availability, with network attack vector, low privileges required, and no user interaction needed. No public exploits have been reported yet, but the risk is significant given the widespread use of WordPress and this popular plugin.

The impact of CVE-2024-4157 is substantial for organizations using the affected WordPress plugin. Successful exploitation can lead to remote code execution, enabling attackers to take full control of the affected WordPress site. This could result in data breaches, website defacement, malware distribution, or pivoting to internal networks. Arbitrary file deletion could disrupt website availability and integrity, causing downtime and loss of user trust. Sensitive data exposure could include user information or credentials stored on the site. The requirement for authenticated access limits exposure but does not eliminate risk, especially in environments with multiple contributors or weak access controls. The ability to bypass permission requirements by chaining with another vulnerability (CVE-2024-2771) further escalates the threat, potentially allowing attackers to exploit the vulnerability without strict permissions. Given WordPress's extensive global use, this vulnerability poses a significant risk to a wide range of organizations, from small businesses to large enterprises relying on WordPress for their web presence.

1. Immediate patching: Update the Contact Form Plugin by Fluent Forms to a version that addresses this vulnerability once available. Monitor vendor announcements for patches. 2. Restrict permissions: Review and limit user roles and permissions in WordPress, ensuring only trusted users have contributor-level or higher access, and carefully control "View Form" and "Manage Form" permissions. 3. Plugin and theme audit: Evaluate installed plugins and themes for potential gadget chains that could be exploited in conjunction with this vulnerability, and remove or update insecure components. 4. Implement Web Application Firewall (WAF) rules: Deploy WAF rules to detect and block suspicious deserialization payloads targeting this plugin. 5. Monitor logs: Enable detailed logging and monitor for unusual activity related to form management or deserialization attempts. 6. Harden WordPress environment: Follow best practices for WordPress security, including limiting plugin installations, using least privilege principles, and isolating critical systems. 7. Incident response readiness: Prepare to respond quickly to any signs of exploitation, including backups and recovery plans. 8. Consider disabling or replacing the vulnerable plugin if immediate patching is not feasible.