The Popup Builder plugin for WordPress suffers from a stored cross-site scripting vulnerability (CWE-79) due to improper neutralization of input during web page generation. Specifically, the plugin fails to adequately sanitize and escape user-supplied attributes in its custom JavaScript feature, allowing authenticated users with contributor or higher privileges to inject malicious scripts. These scripts execute in the context of any user who accesses the compromised page, potentially leading to session hijacking or other script-based attacks. The vulnerability affects all versions up to 4.2.7. The CVSS 3.1 base score is 6.4, reflecting network attack vector, low attack complexity, privileges required, no user interaction, and partial confidentiality and integrity impact.

An attacker with contributor-level or higher access can inject persistent malicious JavaScript code into pages generated by the Popup Builder plugin. This code executes in the browsers of users who view the infected pages, potentially leading to unauthorized actions such as session hijacking or data manipulation. The confidentiality and integrity of user data can be partially compromised. There is no impact on availability. No known active exploitation has been reported.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict contributor-level access to trusted users only and consider disabling the custom JavaScript functionality if possible. Monitor for plugin updates from the vendor that address this vulnerability.