The MailOptin – Popup, Optin Forms & Email Newsletters for Mailchimp, HubSpot, AWeber plugin for WordPress suffers from a stored cross-site scripting vulnerability due to insufficient input sanitization and output escaping in the 'post-meta' shortcode. This allows authenticated users with contributor-level privileges or above to inject arbitrary JavaScript code into pages, which executes when those pages are accessed by others. The vulnerability affects all versions up to and including 1.2.70.3. The CVSS 3.1 base score is 5.4, reflecting a medium severity with network attack vector, low attack complexity, and partial impact on confidentiality and integrity.

Successful exploitation allows an authenticated contributor or higher to inject malicious scripts into pages, potentially leading to unauthorized actions or data exposure when other users view the infected content. The impact is limited to confidentiality and integrity with no availability impact. There are no known active exploits in the wild at this time.

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 or limiting use of the 'post-meta' shortcode. Monitor official vendor channels for updates and apply patches promptly once released.