Simple Custom Login Page <= 1.0.3 - Authenticated (Admin+) Stored Cross-Site Scripting
Strategic Overview
- Status
- Patched in 1.0.4
- Affected Plugin
- Simple Custom Login Page
- Affected Version
<= 1.0.3- CVSS
- 4.4Medium
- Weakness type
- CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- CVE
CVE-2026-10100
At a glance
CVE-2026-10100 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Simple Custom Login Page WordPress plugin, affecting versions <= 1.0.3. It carries a CVSS score of 4.4 (reachable over the network). Exploitation requires an authenticated account at Admin level or above. The issue is fixed in version 1.0.4; sites on affected versions should update now. Disclosed June 2026, reported by Nguyen Duong.
Vulnerability Overview
The Simple Custom Login Page plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the color settings fields (Page Background, Form Background, Text Color, Link Color) in versions up to and including 1.0.3. This is due to insufficient input sanitization of the color option values (they were registered with register_setting() and stored via the Settings API/update_option() with no sanitize_callback) combined with the values being output into a <style> block on wp-login.php using esc_attr(), which is incorrect for a CSS context (it does not escape ;, {, }, / or *). This makes it possible for authenticated attackers, with administrator-level access and above, to inject arbitrary CSS rules into the login page that are rendered for all unauthenticated visitors, enabling UI-redress and credential-phishing attacks.
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')
Simple Custom Login Page <= 1.0.3 carries this weakness at register_setting(), and reaching it takes an account at Admin 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 Simple Custom Login Page the fix is 1.0.4: builds <= 1.0.3 are affected, anything from 1.0.4 onward is not.
Remediation
Update to version 1.0.4, or a newer patched version
How does WordSec protect against this?
An attacker needs Admin 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: Simple Custom Login Page 1.0.4 closes this, and updating the plugin is the step that ends it.
- Firewall
- Alerts
External References
Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C