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Cross-site Scripting (XSS)Weakness · CWE-79

CVE-2026-4279

MEDIUM · 6.4 CVSS v3.1 Published 2026-04-22
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
70/100
Remediation priority · Elevated
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The Bread & Butter WordPress plugin suffers from a Stored XSS vulnerability in the customEventShortCodeButton() function. The 'event' shortcode attribute is not sanitized or escaped when rendered in an onclick HTML attribute, allowing injection of arbitrary JavaScript. Authenticated attackers with Contributor-level access can embed malicious scripts that execute when users click the injected button.

MitigationUpdate the Bread & Butter plugin to a version beyond 8.2.0.25 that applies esc_attr() or esc_js() to the 'event' attribute, or manually patch the customEventShortCodeButton() function to use proper escaping.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm Bread & Butter plugin is installed
    In WordPress admin, go to Plugins > Installed Plugins and look for 'Bread & Butter' plugin, or inspect the wp-content/plugins directory for a folder named 'bread-and-butter' or similar
    Affected if The plugin is not installed or not present in the WordPress environment
  2. Identify the installed plugin version
    In WordPress admin, go to Plugins > Installed Plugins and find the Bread & Butter plugin; the version number is displayed below the plugin name
    Affected if The installed version is 8.2.0.25 or lower, or if the version cannot be determined and the plugin is present
  3. Locate the customEventShortCodeButton() function
    Access the plugin files via FTP or file manager; search for 'customEventShortCodeButton' in PHP files within the plugin directory, typically in a shortcode or button handler file
    Affected if The function exists and contains code that outputs the 'event' parameter directly into an onclick attribute without escaping (look for echo or print statements placing the event value into HTML)
  4. Inspect shortcode usage for the vulnerable 'event' attribute
    Search WordPress post content in the database for '[bread_and_butter' or similar shortcode containing 'event=' attribute, or check page source for onclick handlers that may contain unsanitized input
    Affected if A shortcode with an 'event' attribute is present and the rendered HTML shows unescaped characters in an onclick handler
  5. Verify if Contributor-level or higher users exist
    In WordPress admin, go to Users and review roles; check if any users have Contributor, Author, Editor, or Administrator roles who could create or edit content with shortcodes
    Affected if Any authenticated user with Contributor-level or higher access exists in the WordPress site

You are affected if the Bread & Butter plugin is installed with version 8.2.0.25 or lower AND the customEventShortCodeButton function renders the 'event' attribute without esc_attr() or esc_js() escaping in an onclick HTML attribute.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update the Bread & Butter plugin to a version beyond 8.2.0.25 that applies esc_attr() or esc_js() to the 'event' attribute, or manually patch the customEventShortCodeButton() function to use proper escaping.

Have this fixed Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-4279 in production — separate from our analysis above.

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