The EmbedPress plugin for WordPress, which enables embedding PDFs, YouTube videos, and other media, contains a stored XSS vulnerability (CWE-79) in the 'embedpress_calendar' shortcode. This flaw allows authenticated users with contributor or higher privileges to inject arbitrary web scripts due to improper input neutralization and output escaping. The vulnerability affects all versions up to and including 3.9.14. Exploitation results in script execution in the context of users visiting the compromised pages, potentially leading to session hijacking or other client-side impacts. The CVSS 3.1 base score is 6.4, reflecting network attack vector, low attack complexity, required privileges, no user interaction, and partial confidentiality and integrity impact.

An attacker with contributor-level or higher access can inject persistent malicious scripts into pages via the vulnerable shortcode. These scripts execute in the browsers of users who view the infected pages, potentially compromising user sessions or performing unauthorized actions within the context of affected users. The impact is limited to confidentiality and integrity loss, with no availability impact reported. No evidence of active exploitation in the wild is currently known.

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 removing the EmbedPress plugin if not essential. Monitor official wpdevteam channels for updates and apply patches promptly once available.