The Eventer plugin for WordPress suffers from a stored cross-site scripting vulnerability due to improper neutralization of input during web page generation. Specifically, user-supplied attributes in shortcodes are not adequately sanitized or escaped, enabling authenticated users with contributor or higher privileges to inject arbitrary JavaScript code. This code executes in the context of any user visiting the compromised page, potentially leading to session hijacking or other script-based attacks. The vulnerability affects versions up to and including 3.9.9.4 and has a CVSS 3.1 base score of 6.4 (AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N).

An attacker with contributor-level or higher permissions can inject persistent malicious scripts into pages via shortcode attributes. These scripts execute in the browsers of users who view the infected pages, potentially leading to information disclosure or manipulation of user sessions. The vulnerability does not allow denial of service or privilege escalation beyond the contributor role. There are no known 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 permissions to trusted users only and consider disabling shortcode usage from untrusted sources. Monitor for updates from the plugin vendor regarding patches or official mitigations.