CVE-2025-4587 is a stored Cross-Site Scripting (XSS) vulnerability identified in the A/B Testing for WordPress plugin developed by johnjamesjacoby. The vulnerability exists in all versions up to and including 1.18.2 due to improper neutralization of input during web page generation, specifically in the 'ab-testing-for-wp/ab-test-block' block. The root cause is insufficient sanitization and escaping of the 'id' parameter, which is used in the plugin's block rendering process. An authenticated attacker with contributor-level privileges or higher can exploit this flaw by injecting arbitrary JavaScript code into the 'id' parameter. Because the injected script is stored, it executes every time a user visits the affected page, potentially compromising user sessions, stealing cookies, or performing actions on behalf of users. The vulnerability does not require user interaction beyond visiting the page, and the attacker needs only contributor-level access, which is a relatively low privilege level in WordPress. The CVSS 3.1 base score is 6.4, reflecting medium severity with network attack vector, low attack complexity, and privileges required. The scope is changed, as the vulnerability affects components beyond the attacker’s privileges. No public exploits have been reported yet, but the risk remains significant given the widespread use of WordPress and the plugin. The vulnerability is categorized under CWE-79, which covers improper input neutralization leading to XSS. No official patches or updates were linked at the time of publication, so mitigation may require manual intervention or disabling the vulnerable plugin.

This vulnerability can lead to significant security risks for organizations using the affected plugin on WordPress sites. An attacker with contributor-level access can inject malicious scripts that execute in the context of any user visiting the compromised page, including administrators. This can result in session hijacking, unauthorized actions, defacement, or distribution of malware. The compromise of user credentials or site integrity can damage organizational reputation, lead to data breaches, and cause operational disruptions. Since contributor-level access is often granted to trusted users or external content creators, the attack surface is broader than vulnerabilities requiring administrative privileges. The stored nature of the XSS means the malicious payload persists and can affect multiple users over time. Organizations with high-traffic websites or those handling sensitive user data are particularly at risk. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, especially as exploit code may emerge. The medium CVSS score reflects a moderate but actionable threat that requires timely remediation to prevent exploitation.

Organizations should immediately assess their WordPress installations for the presence of the A/B Testing for WordPress plugin and verify the version in use. If running version 1.18.2 or earlier, they should disable or remove the plugin until a security patch is available. In the absence of an official patch, administrators can implement manual mitigations such as applying strict input validation and output escaping on the 'id' parameter within the plugin code, or restricting contributor-level user permissions to trusted individuals only. Monitoring and auditing contributor activity for suspicious input or changes can help detect attempted exploitation. Employing Web Application Firewalls (WAFs) with custom rules to detect and block malicious script injections targeting the vulnerable parameter can provide temporary protection. Additionally, organizations should educate contributors about the risks of injecting untrusted content and enforce the principle of least privilege. Regular backups and incident response plans should be updated to handle potential XSS incidents. Finally, organizations should stay alert for official patches or updates from the plugin developer and apply them promptly once released.