CVE-2024-1987 is a stored cross-site scripting (XSS) vulnerability identified in the WP-Members Membership Plugin for WordPress, developed by cbutlerjr. This vulnerability affects all plugin versions up to and including 3.4.9.1. The root cause is improper neutralization of script-related HTML tags (CWE-80) due to insufficient input sanitization and output escaping on user-supplied attributes within the plugin's shortcode functionality. Authenticated users with contributor-level or higher permissions can exploit this flaw by injecting arbitrary JavaScript code into pages via shortcode attributes. Because the malicious script is stored persistently, it executes whenever any user accesses the infected page, potentially compromising user sessions, stealing cookies, or performing unauthorized actions on behalf of users. The vulnerability does not require user interaction beyond page access and has a CVSS v3.1 base score of 6.4, indicating medium severity. The attack vector is network-based with low complexity, requiring privileges but no user interaction. The scope is changed (S:C) because the vulnerability affects resources beyond the attacker’s privileges by impacting other users. There are no known public exploits or patches currently available, emphasizing the need for proactive mitigation. This vulnerability is particularly concerning for sites with multiple contributors and public membership areas, as it can facilitate privilege escalation or persistent compromise of user accounts and site integrity.

The impact of CVE-2024-1987 is significant for organizations using the WP-Members Membership Plugin, especially those with multiple contributors or public-facing membership sites. Successful exploitation allows attackers to inject persistent malicious scripts that execute in the browsers of site visitors, potentially leading to session hijacking, theft of sensitive information, unauthorized actions performed with victim user privileges, and defacement or redirection attacks. This undermines user trust and can lead to reputational damage, data breaches, and compliance violations. Since the vulnerability requires contributor-level access, attackers may leverage compromised or weak contributor accounts to escalate their impact. The scope change means that the attack affects users beyond the attacker’s privileges, increasing the risk of widespread compromise. Although no known exploits are reported in the wild, the ease of exploitation and medium CVSS score suggest that attackers could weaponize this vulnerability. Organizations relying on this plugin for membership management are at risk of targeted attacks, especially in sectors with sensitive user data or high-value memberships.

To mitigate CVE-2024-1987, organizations should first verify if they are using the WP-Members Membership Plugin version 3.4.9.1 or earlier and plan immediate updates once a patched version is released. In the absence of an official patch, administrators should restrict contributor-level permissions to trusted users only and audit existing contributor accounts for suspicious activity. Implementing a Web Application Firewall (WAF) with custom rules to detect and block malicious script payloads in shortcode attributes can reduce risk. Additionally, site administrators can temporarily disable shortcode usage or restrict shortcode attribute inputs via custom code filters to sanitize inputs more aggressively. Enforcing strong authentication and monitoring user activity logs for anomalous behavior can help detect exploitation attempts early. Regular security scanning and penetration testing focused on XSS vulnerabilities in membership areas are recommended. Finally, educating contributors about secure input practices and the risks of injecting untrusted content can reduce accidental exploitation.