CVE-2026-4279

The record

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.

Affected packages

Related vulnerabilities

• CVE-2026-96379 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96382 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96368 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96361 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96362 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96360 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96357 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96358 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79