What is CVE-2026-103999?

CVE-2026-103999 is a high-severity vulnerability in Themefic Ultra Addons For Contact Form 7, classified under Cross-site Scripting. CVSS score: 7.2/10. Published 2026-10-16.

How severe is CVE-2026-103999?

High severity. CVSS v3 base score is 7.2 out of 10.

XSS in Themefic Ultra Addons For Contact Form 7

CVE-2026-103999

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.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2026-10-16 · last modified 2026-10-16.

CVSS v3 metric

CVSS v3 base score 7.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Themefic Ultra Addons For Contact Form 7

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

Frequently asked questions

What is CVE-2026-103999?: CVE-2026-103999 is a high-severity vulnerability in Themefic Ultra Addons For Contact Form 7, classified under Cross-site Scripting. CVSS score: 7.2/10. Published 2026-10-16.
How severe is CVE-2026-103999?: High severity. CVSS v3 base score is 7.2 out of 10.