CVE-2025-8871 is a deserialization vulnerability classified under CWE-502 affecting the Everest Forms Pro WordPress plugin versions up to 1.9.7. The vulnerability arises from unsafe deserialization of untrusted data passed to the PHP function mime_content_type(), which can be manipulated by unauthenticated attackers through specially crafted form submissions. Specifically, if a form on the site includes a non-required signature field alongside an image upload field, attackers can inject a malicious PHP object. However, the vulnerability alone does not guarantee code execution or other severe impacts because no gadget POP (Property Oriented Programming) chain is present within the vulnerable plugin itself. Exploitation requires the presence of another installed plugin or theme that contains a POP chain to leverage the injected object for malicious actions such as arbitrary file deletion, sensitive data disclosure, or remote code execution. This vulnerability is only exploitable on PHP versions prior to 8, as PHP 8 introduced changes that mitigate this attack vector. The vulnerability was published in November 2025 with a CVSS 3.1 base score of 5.6, indicating medium severity. No public exploits have been reported yet, but the risk increases in complex WordPress environments with multiple plugins and themes that may provide the necessary POP chains. The vulnerability highlights the risks of unsafe deserialization in PHP applications and the importance of secure coding practices and environment hardening.

The impact of CVE-2025-8871 depends heavily on the environment in which Everest Forms Pro is deployed. On its own, the vulnerability allows injection of PHP objects but does not directly lead to code execution or data compromise. However, in WordPress installations where additional plugins or themes contain gadget POP chains, attackers can leverage this vulnerability to perform critical actions such as deleting arbitrary files, accessing sensitive information, or executing arbitrary code remotely. This could lead to website defacement, data breaches, or full server compromise. Since the vulnerability is exploitable without authentication, any public-facing WordPress site using the affected plugin on PHP versions prior to 8 is at risk if the required conditions are met. The medium CVSS score reflects the moderate likelihood and impact, but the potential for severe consequences in complex environments makes this a significant threat. Organizations with high-value WordPress sites, especially those handling sensitive user data or critical business functions, face increased risk. The absence of known exploits in the wild currently reduces immediate threat but does not eliminate the risk of future exploitation.

To mitigate CVE-2025-8871, organizations should first upgrade Everest Forms Pro to a version that addresses this vulnerability once available. Until a patch is released, administrators should consider the following specific actions: (1) Disable or remove any non-required signature fields and image upload fields in forms to prevent the attack vector. (2) Audit all installed plugins and themes for the presence of gadget POP chains that could be exploited in conjunction with this vulnerability, removing or updating those that pose a risk. (3) Upgrade PHP to version 8 or higher, as the vulnerability is not exploitable on PHP 8+. (4) Implement web application firewall (WAF) rules to detect and block suspicious serialized payloads targeting form submissions. (5) Restrict file upload capabilities and validate uploaded content rigorously to reduce attack surface. (6) Monitor logs for unusual activity related to form submissions or deserialization attempts. (7) Employ principle of least privilege for WordPress file and directory permissions to limit impact if exploitation occurs. These targeted mitigations go beyond generic advice by focusing on the specific conditions required for exploitation and the environment factors that enable it.