The Event post plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's events_cal shortcode in all versions up to, and including, 5.9.6 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in N.O.U.S. Open Useful and Simple Event post allows Stored XSS.This issue affects Event post: from n/a through 5.8.6.