CVE-2026-10100 Simple Custom Login Page <= 1.0.3 - Authenticated (Admin+) Stored Cross-Site Scripting
Administrators can inject malicious CSS into the WordPress login page, enabling UI-redress and credential phishing attacks against unauthenticated visitors.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-10100?
CVE-2026-10100 is a medium-severity cross-site scripting vulnerability in pattihis Simple Custom Login Page, published on 2 Jun 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
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.
Weakness: CWE-79
Which versions are affected by CVE-2026-10100?
How do I fix CVE-2026-10100?
No fix has been published for CVE-2026-10100 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-2026-10100 being exploited?
There is no known exploitation of CVE-2026-10100 in the wild and no public exploit code.
Sources
Also known as GHSA-855q-xm3j-j7h8.