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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
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
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.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-103999 being exploited?
There is no known exploitation of CVE-2026-103999 in the wild and no public exploit code.
Sources
Also known as GHSA-3658-jvcq-xc7g.