CVE-2026-38931: SimplePhp XSS Vulnerability

CVE-2026-38931 Overview

CVE-2026-38931 is a stored cross-site scripting (XSS) vulnerability in the /admin/config-module.php component of the creatorsofcode SimplePHP application. The flaw exists in GitHub commit 5184cff, identified as the latest commit as of 2026-02-27. Attackers with low-privilege access can inject a crafted payload that persists in the application and executes in the browser of any user who later views the affected page. The vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation.

Critical Impact
An authenticated attacker can store malicious JavaScript that executes in other users' browsers, enabling session theft, UI redress, and pivoting against administrative accounts.

Affected Products

creatorsofcode SimplePHP at GitHub commit 5184cff
SimplePHP /admin/config-module.php component
All SimplePHP deployments tracking the latest commit as of 2026-02-27

Discovery Timeline

2026-05-27 - CVE-2026-38931 published to NVD
2026-05-27 - Last updated in NVD database

Technical Details for CVE-2026-38931

Vulnerability Analysis

The vulnerability resides in /admin/config-module.php, an administrative endpoint of the SimplePHP application. User-supplied input submitted to this component is stored without proper output encoding or input sanitization. When the stored value is later rendered in an HTML response, the browser interprets injected markup as executable script.

Because the payload is persistent, every visitor to the affected page receives the malicious content. The scope change in the impact profile indicates that injected script can reach resources beyond the vulnerable component, including authenticated sessions in the same browser context. Exploitation requires both low-privilege authentication and a user interaction step to trigger the payload.

Root Cause

The root cause is improper neutralization of input during web page generation [CWE-79]. The config-module.php handler accepts attacker-controlled values, writes them to persistent storage, and later emits them into HTML output without applying contextual encoding such as HTML entity escaping. No allowlist-based input validation is applied at submission time.

Attack Vector

An authenticated attacker with access to the admin module configuration interface submits a crafted payload containing HTML or JavaScript markup. The payload is stored server-side by /admin/config-module.php. When another authenticated user, typically an administrator, browses the affected page, the script executes in their session context. This enables cookie theft, forced administrative actions, credential harvesting via injected forms, and lateral movement within the application.

No verified proof-of-concept code is published. Technical write-up details are available at the Moworn CVE-2026-38931 Post.

Detection Methods for CVE-2026-38931

Indicators of Compromise

HTTP POST requests to /admin/config-module.php containing <script>, onerror=, onload=, or javascript: substrings in request bodies
Unexpected outbound requests from administrator browsers to attacker-controlled domains following visits to the module configuration page
Stored configuration values in SimplePHP database tables containing HTML tags or JavaScript event handlers

Detection Strategies

Inspect web server access logs for POST submissions to /admin/config-module.php and correlate with the authenticated user identity
Run database queries against module configuration tables to surface entries containing angle brackets, script, or event handler keywords
Deploy a web application firewall rule that flags XSS payload signatures on requests targeting administrative PHP endpoints

Monitoring Recommendations

Enable verbose request body logging for all /admin/* endpoints in SimplePHP deployments
Monitor administrator session activity for anomalous client-side behavior such as unexpected XHR or fetch calls after page loads
Alert on Content Security Policy (CSP) violation reports if a reporting endpoint is configured

How to Mitigate CVE-2026-38931

Immediate Actions Required

Restrict access to /admin/config-module.php to trusted administrator IP ranges using web server access controls
Audit existing module configuration records for stored HTML or JavaScript payloads and remove malicious entries
Rotate administrator credentials and session tokens if injected payloads are discovered

Patch Information

No vendor patch is referenced in the NVD entry for CVE-2026-38931. SimplePHP operators should monitor the creatorsofcode project page and the SimplePHP project site for updated commits that address the input handling in /admin/config-module.php. Until a fixed commit is published, apply the workarounds below.

Workarounds

Apply server-side HTML entity encoding to all output rendered from the module configuration store, using PHP's htmlspecialchars() with ENT_QUOTES and the correct character set
Add an input allowlist that rejects angle brackets and JavaScript event handler patterns in submissions to /admin/config-module.php
Deploy a strict Content Security Policy that disables inline script execution on administrative pages

bash

# Configuration example: nginx CSP header for SimplePHP admin paths
location /admin/ {
    add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'none'" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header X-Frame-Options "DENY" always;
}