# CVE-2026-3551: Cross-site scripting in Custom New User Notification

> Administrators can inject scripts via plugin settings, potentially targeting super admins in multi-site installations.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Apr 2026
- **Updated:** 16 Apr 2026
- **Also known as:** GHSA-4xx2-h7jh-g7ph

## What is CVE-2026-3551?

CVE-2026-3551 is a medium-severity cross-site scripting vulnerability in rafasashi Custom New User Notification, published on 16 Apr 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official 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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-3551?


## How do I fix CVE-2026-3551?

No fix has been published for CVE-2026-3551 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-3551 being exploited?

There is no known exploitation of CVE-2026-3551 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3551 and fix it if it is affected.

What it is: CVE-2026-3551 is a medium-severity cross-site scripting vulnerability in rafasashi Custom New User Notification, published on 16 Apr 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-3551 in the wild and no public exploit code.

Affected product: rafasashi Custom New User Notification. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-3551/ (Markdown: https://insights.sbomify.com/CVE-2026-3551/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3551
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3551
- OSV: https://osv.dev/vulnerability/CVE-2026-3551

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3551/
Summaries are generated and may contain mistakes; the official description above is the record.