Stored Cross‑Site Scripting (XSS) occurs when the 'breadbutter-customevent-button' shortcode accepts an 'event' attribute that is not sanitized. The value is inserted directly into an onclick attribute of a JavaScript string without escaping. A compromised value allows an authenticated contributor‑level user to inject malicious JavaScript that runs when any page visitor clicks the button. The CWE for this flaw is 79.

All editions of the Bread & Butter WordPress plugin from original release through and including version 8.2.0.25 are affected. The flaw can be exercised on any WordPress installation that has the plugin installed and an authenticated user with Contributor or higher privileges. Only the authenticated user can inject the payload; reflected or unauthenticated attacks are not supported by the current code.

The CVSS base score of 6.4 indicates a moderate severity vulnerability, and the EPSS score is not available. The exploit requires the attacker to log in as a Contributor or higher, and it targets the web application layer rather than the network. Because the payload is stored in a page and triggers upon a button click, an attacker can potentially steal session cookies, deface content, or perform other malicious actions. The vulnerability is listed in no CISA KEV catalog, but the moderate CVSS and the requirement for authenticated access still make it a notable security concern for site administrators.