CVE-2026-4279

The Bread & Butter plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'breadbutter-customevent-button' shortcode in all versions up to, and including, 8.2.0.25. This is due to insufficient input sanitization and output escaping on the 'event' shortcode attribute. The customEventShortCodeButton() function takes the 'event' attribute value and directly interpolates it into a JavaScript string within an onclick HTML attribute without applying esc_attr() or esc_js(). Notably, the sister function customEventShortCode() properly uses esc_js() for the same attribute, but this was omitted in the button variant. 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 the page and clicks the injected button.

• CWE-79

• https://plugins.trac.wordpress.org/browser/bread-butter/tags/8.2.0.25/src/Base/Shortcode.php#L364
• https://plugins.trac.wordpress.org/browser/bread-butter/tags/8.2.0.25/src/Base/Shortcode.php#L380
• https://plugins.trac.wordpress.org/browser/bread-butter/trunk/src/Base/Shortcode.php#L364
• https://plugins.trac.wordpress.org/browser/bread-butter/trunk/src/Base/Shortcode.php#L380
• https://www.wordfence.com/threat-intel/vulnerabilities/id/0728b42b-5ec7-46a2-a9a5-3316107e9324?source=cve

Published

Apr 22, 2026

Last Modified

Jun 17, 2026

Status

Deferred

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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