CVE-2025-4587 is a stored Cross-Site Scripting (XSS) vulnerability affecting the 'A/B Testing for WordPress' plugin developed by johnjamesjacoby, specifically in all versions up to and including 1.18.2. The vulnerability arises due to improper input sanitization and output escaping of the 'id' parameter within the plugin's 'ab-testing-for-wp/ab-test-block' block. Authenticated users with contributor-level permissions or higher can exploit this flaw by injecting malicious JavaScript code into pages managed by the plugin. Because the malicious script is stored persistently, it executes whenever any user accesses the compromised page, potentially leading to session hijacking, privilege escalation, or unauthorized actions performed in the context of the victim's browser session. The vulnerability has a CVSS 3.1 base score of 6.4, indicating a medium severity level. The attack vector is network-based with low attack complexity, requiring privileges equivalent to contributor access but no user interaction. The scope is changed, meaning the vulnerability can affect resources beyond the initially compromised component. No known exploits are currently reported in the wild, and no official patches have been linked yet. This vulnerability falls under CWE-79, which is a common and well-understood class of web application security issues related to improper neutralization of input during web page generation.

For European organizations using WordPress sites with the vulnerable A/B Testing plugin, this vulnerability poses a significant risk to the confidentiality and integrity of their web applications. An attacker with contributor-level access could inject malicious scripts that execute in the browsers of site visitors or administrators, potentially stealing session cookies, redirecting users to malicious sites, or performing unauthorized actions on behalf of users with higher privileges. This can lead to data breaches, defacement, loss of customer trust, and regulatory non-compliance, especially under GDPR requirements concerning personal data protection. Since WordPress is widely used across Europe for corporate, governmental, and e-commerce websites, exploitation could disrupt business operations and damage reputations. The vulnerability does not directly affect availability but the indirect consequences of exploitation, such as site defacement or unauthorized changes, could cause service disruptions. The requirement for authenticated contributor-level access limits the attack surface but insider threats or compromised accounts could facilitate exploitation.

European organizations should immediately audit their WordPress installations to identify the presence of the vulnerable 'A/B Testing for WordPress' plugin. Until an official patch is released, mitigation should include restricting contributor-level access to trusted users only and implementing strict user account management policies, including multi-factor authentication to reduce the risk of account compromise. Web application firewalls (WAFs) can be configured to detect and block suspicious payloads targeting the 'id' parameter in the vulnerable block. Additionally, organizations should implement Content Security Policy (CSP) headers to limit the impact of injected scripts. Regular security scanning and monitoring for unusual activity on WordPress sites are recommended. Once a patch is available, prompt application of updates is critical. Developers and site administrators should also review custom code or integrations that interact with the plugin to ensure proper input validation and output encoding practices are followed.