CVE-2025-3421 is a reflected Cross-Site Scripting (XSS) vulnerability identified in the Everest Forms plugin for WordPress, which is used to create contact forms, quizzes, surveys, newsletters, and payment forms. The vulnerability exists due to insufficient sanitization and escaping of the 'form_id' parameter in all versions up to and including 3.1.1. This flaw allows unauthenticated attackers to craft malicious URLs containing JavaScript payloads that, when clicked by a victim, execute in the context of the affected website. The vulnerability is classified under CWE-79, indicating improper neutralization of input during web page generation. The CVSS v3.1 base score is 6.1, reflecting a medium severity with an attack vector of network (remote), low attack complexity, no privileges required, but requiring user interaction. The scope is changed (S:C), meaning the vulnerability can affect resources beyond the vulnerable component. The impact affects confidentiality and integrity but not availability. No patches or exploit code are currently publicly available, and no known exploits in the wild have been reported. However, the vulnerability poses risks such as session hijacking, credential theft, and redirection to malicious sites if exploited. The plugin's widespread use in WordPress sites makes this a relevant threat to many web administrators and users.

The primary impact of CVE-2025-3421 is on the confidentiality and integrity of user data and sessions on affected WordPress sites. Successful exploitation can lead to theft of cookies, session tokens, or other sensitive information, enabling attackers to impersonate users or administrators. It can also facilitate phishing attacks by injecting malicious scripts that alter webpage content or redirect users to fraudulent sites. Although availability is not directly affected, the reputational damage and potential data breaches can have significant business consequences. Organizations relying on Everest Forms for customer interactions, surveys, or payments may face increased risk of data compromise and loss of user trust. Since the vulnerability requires user interaction, social engineering is a key factor in exploitation, increasing the risk for sites with high user engagement. The medium CVSS score reflects that while the attack is feasible and impactful, it is not trivially exploitable without user action. The global prevalence of WordPress and this plugin means the threat can affect organizations of all sizes and sectors worldwide.

To mitigate CVE-2025-3421, organizations should immediately update the Everest Forms plugin to a version that addresses this vulnerability once available. In the absence of an official patch, administrators can implement web application firewall (WAF) rules to detect and block suspicious requests containing malicious payloads in the 'form_id' parameter. Input validation and output encoding should be enforced at the application level to neutralize script injection attempts. Site owners should educate users about the risks of clicking untrusted links and consider implementing Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts. Regular security audits and monitoring for unusual activity related to form submissions or URL parameters can help detect exploitation attempts. Additionally, restricting plugin usage to trusted users and minimizing plugin footprint reduces attack surface. Backup and incident response plans should be updated to handle potential XSS incidents. Collaboration with plugin developers and timely application of security updates remain critical.