WordPress Core <= 7.1 - Authenticated (Administrator+) Stored Cross-Site Scripting via Custom Header Image Data

2026-09-17 00:00
Jeremy Felt

Strategic Overview

Status
Patched in 6.6.8
Affected Core
WordPress 7.1
Affected Version
6.6.7 – 7.1 · 6 branches
CVSS
4.4Medium
Weakness type
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE
CVE pending
View all WordPress 7.1 vulnerabilities

At a glance

This record tracks a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the WordPress 7.1 WordPress release line, affecting 6.6.7 – 7.1 · 6 branches. It carries a CVSS score of 4.4 (reachable over the network). Exploitation requires an authenticated account at Administrator level or above. The issue is fixed in version 6.6.8; sites on affected versions should update now. Disclosed September 2026, reported by Jeremy Felt.

Vulnerability Overview

WordPress Core is vulnerable to Stored Cross-Site Scripting via the custom header 'header_image_data' theme mod in various versions up to, and including, 7.1 due to insufficient sanitization of the header image width/height/URL values and an unescaped style attribute in the custom-header admin screen. get_custom_header() returned width/height without integer casting and Custom_Image_Header::step_1() echoed the style string without escaping. This makes it possible for authenticated attackers with edit_theme_options capability to inject web scripts; primarily relevant on Multisite where site administrators lack unfiltered_html.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, and no interaction from a victim user.

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

WordPress 7.1 6.6.7 – 7.1 · 6 branches carries this weakness at header_image_data, and reaching it takes an account at Administrator level or above. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.

Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For WordPress 7.1 the fix is 6.6.8: builds 6.6.7 – 7.1 · 6 branches are affected, anything from 6.6.8 onward is not.

Remediation

Update to one of the following versions, or a newer patched version: 6.6.8, 6.7.8, 6.8.9, 6.9.8, 7.0.5, 7.1.1

How does WordSec protect against this?

An attacker needs Administrator access first, so the firewall sees the attempt as traffic from a logged-in account: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: updating to 6.6.8 is the step that ends it.

  • Firewall
  • Alerts

External References

https://www.wordfence.com/threat-intel/vulnerabilities/id/3d59700b-3540-464c-bd27-23bb71f9b082

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