CVE-2025-6831 is a stored Cross-Site Scripting (XSS) vulnerability identified in the wpeverest User Registration & Membership plugin for WordPress, which is widely used for custom registration forms, login forms, user profiles, content restriction, and membership management. The vulnerability exists due to improper neutralization of input during web page generation, specifically within the plugin's urcr_restrict shortcode. This shortcode fails to adequately sanitize and escape user-supplied attributes, allowing authenticated attackers with contributor-level or higher privileges to inject arbitrary JavaScript code into pages. Because the malicious script is stored, it executes every time a user views the affected page, potentially compromising user sessions, stealing cookies, or performing actions on behalf of users with elevated privileges. The vulnerability has a CVSS 3.1 base score of 6.4, indicating medium severity, with an attack vector of network, low attack complexity, requiring privileges (PR:L), no user interaction, and a scope change (S:C). The impact affects confidentiality and integrity but not availability. No public exploits have been reported yet, but the vulnerability is significant due to the common use of the plugin and the ease with which authenticated users can exploit it. The flaw affects all plugin versions up to 4.2.4. The vulnerability was reserved on June 27, 2025, and published on July 22, 2025. The plugin is developed by wpeverest and is popular among WordPress site administrators for membership and user management functionalities.

The impact of CVE-2025-6831 is primarily on the confidentiality and integrity of affected WordPress sites. An attacker with contributor-level access can inject malicious scripts that execute in the context of other users visiting the compromised pages. This can lead to session hijacking, theft of sensitive information such as cookies or credentials, unauthorized actions performed on behalf of other users, and potential privilege escalation if administrative users are targeted. While availability is not directly affected, the injected scripts could be used to deface websites or redirect users to malicious sites, damaging organizational reputation. Since WordPress powers a significant portion of the web, including many business, educational, and governmental sites, the vulnerability poses a risk to a broad range of organizations worldwide. The requirement for authenticated access limits exploitation to insiders or users with some level of trust, but contributor roles are commonly assigned in many WordPress environments, increasing the attack surface. The scope change in the CVSS vector indicates that the vulnerability can affect resources beyond the initially vulnerable component, potentially impacting the entire site or user base.

To mitigate CVE-2025-6831, organizations should take the following specific actions: 1) Immediately update the wpeverest User Registration & Membership plugin to a patched version once available; if no patch is currently released, consider temporarily disabling or removing the plugin to prevent exploitation. 2) Restrict contributor-level permissions and review user roles to ensure that only trusted users have the ability to submit content or use shortcodes that can be exploited. 3) Disable or restrict usage of the urcr_restrict shortcode in all site content until the vulnerability is resolved. 4) Implement Web Application Firewall (WAF) rules to detect and block suspicious script injections related to this plugin. 5) Conduct thorough audits of existing site content for injected scripts or suspicious shortcode usage. 6) Educate site administrators and content contributors about the risks of XSS and the importance of input validation. 7) Monitor logs and user activity for signs of exploitation attempts or unusual behavior. 8) Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts on the site. These measures, combined with prompt patching, will reduce the risk of exploitation and protect site integrity.