Bread & Butter: Content Gating for Verified Leads <= 8.6.0.107 - Authenticated (Contributor+) Stored Cross-Site Scripting via Shortcode Attributes
Strategic Overview
- Status
- Patched in 8.7.0.139
- Affected Version
<= 8.6.0.107- CVSS
- 6.4Medium
- Weakness type
- CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- CVE
CVE-2026-4279
At a glance
CVE-2026-4279 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Bread & Butter WordPress plugin, affecting versions <= 8.6.0.107. It carries a CVSS score of 6.4 (reachable over the network; low attack complexity). Exploitation requires an authenticated account at Contributor level or above. The issue is fixed in version 8.7.0.139; sites on affected versions should update now. Disclosed April 2026, reported by Athiwat Tiprasaharn (Jitlada).
Vulnerability Overview
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, 8.6.0.107. 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.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no interaction from a victim user.
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Bread & Butter <= 8.6.0.107 carries this weakness at breadbutter-customevent-button, and reaching it takes an account at Contributor level or above. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.
Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For Bread & Butter the fix is 8.7.0.139: builds <= 8.6.0.107 are affected, anything from 8.7.0.139 onward is not.
Remediation
Update to version 8.7.0.139, or a newer patched version
How does WordSec protect against this?
An attacker needs Contributor access first, so the firewall sees the attempt as traffic from a logged-in account: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Bread & Butter 8.7.0.139 closes this, and updating the plugin is the step that ends it.
- Firewall
- Alerts
External References
Related records
Same weakness class
Other vulnerabilities in Bread & Butter: Form Conversion, Content Gating & Lead Intelligence
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