The Popup Maker plugin for WordPress, versions up to and including 1.19.0, suffers from a stored cross-site scripting vulnerability (CWE-79) via the 'close_text' parameter. This flaw is due to insufficient input sanitization and output escaping, enabling authenticated users with Contributor-level permissions or higher to inject arbitrary web scripts. These scripts execute in the context of users who access the injected pages, potentially compromising user sessions or data integrity. The vulnerability is network exploitable with low attack complexity and does not require user interaction. The CVSS 3.1 base score is 6.4 (medium severity). No patch or vendor advisory is currently provided, and no known exploits have been reported.

Successful exploitation allows an authenticated attacker with Contributor-level access or higher to inject persistent malicious scripts into pages generated by the Popup Maker plugin. These scripts execute in the browsers of users who visit the affected pages, potentially leading to session hijacking, unauthorized actions, or data theft. The impact affects confidentiality and integrity but does not affect availability. The medium severity score reflects the requirement for authenticated access and the potential for limited impact depending on the victim's privileges.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, restrict Contributor-level access to trusted users only and consider disabling or limiting use of the Popup Maker plugin. Monitor for plugin updates from the vendor and apply any official patches promptly once available.