# CVE-2026-103999: Ultra Addons for Contact Form 7 <= 3.5.54 - Unauthenticated Stored Cross-Site Scripting via File Upload

> Unauthenticated attackers can inject arbitrary web scripts via file upload in Ultra Addons for Contact Form 7, leading to stored XSS.

- **Severity:** High 7.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Oct 2026
- **Updated:** 16 Oct 2026
- **Also known as:** GHSA-3658-jvcq-xc7g

## What is CVE-2026-103999?

CVE-2026-103999 is a high-severity cross-site scripting vulnerability in themefic Ultra Addons for Contact Form 7, published on 16 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The Ultra Addons for Contact Form 7 plugin for WordPress is vulnerable to Stored Cross-Site Scripting via File Upload in all versions up to, and including, 3.5.54 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The extension blocklist gatekeeper is bypassed by uploading text-type files (.txt, .csv, .vtt, .srt, .asc) whose contents begin with an HTML payload such as '<BODY onload=…>', as the check classifies these files as text/plain without inspecting their byte content.

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

## Which versions are affected by CVE-2026-103999?


## How do I fix CVE-2026-103999?

No fix has been published for CVE-2026-103999 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-103999 being exploited?

There is no known exploitation of CVE-2026-103999 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-103999 and fix it if it is affected.

What it is: CVE-2026-103999 is a high-severity cross-site scripting vulnerability in themefic Ultra Addons for Contact Form 7, published on 16 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-103999 in the wild and no public exploit code.

Affected product: themefic Ultra Addons for Contact Form 7. 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-2026-103999/ (Markdown: https://insights.sbomify.com/CVE-2026-103999/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-103999
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-103999
- OSV: https://osv.dev/vulnerability/CVE-2026-103999

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-103999/
Summaries are generated and may contain mistakes; the official description above is the record.