CVE-2025-11125: Online Banking System XSS Vulnerability

CVE-2025-11125 Overview

CVE-2025-11125 is a reflected cross-site scripting (XSS) vulnerability in the langleyfcu Online Banking System. The flaw resides in the Error Message Handler component, specifically in /connection_error.php, where the Error parameter is reflected without proper output encoding. Remote attackers can craft a malicious URL that executes arbitrary JavaScript in a victim's browser when the link is opened. The product follows a rolling release model, so no discrete version identifier is affected — the last known vulnerable commit is 57437e6400ce0ae240e692c24e6346b8d0c17d7a. A public proof of concept has been referenced through VulDB submission #664319.

Critical Impact
Successful exploitation allows attackers to execute arbitrary script in a victim's browser session, enabling credential theft, session hijacking, and phishing against online banking users.

Affected Products

langleyfcu Online Banking System (rolling release)
Codebase up to commit 57437e6400ce0ae240e692c24e6346b8d0c17d7a
Component: /connection_error.php Error Message Handler

Discovery Timeline

2025-09-29 - CVE-2025-11125 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-11125

Vulnerability Analysis

The vulnerability is a reflected cross-site scripting flaw classified under [CWE-79]. The /connection_error.php script receives an Error parameter through user-supplied input and writes its value directly into the HTTP response body. Because the application does not apply HTML entity encoding or context-aware output sanitization, attacker-controlled markup is rendered as executable content by the victim's browser.

The attack requires user interaction. A victim must click a crafted link or visit a page that triggers the request. Once loaded, injected JavaScript executes in the origin of the banking application, giving the attacker access to cookies, DOM content, and any authenticated session state. The EPSS score for this issue is 0.321% at the 24.07 percentile, reflecting a low but non-zero probability of exploitation activity.

Root Cause

The root cause is missing output encoding on a user-controlled query parameter. The Error argument is echoed back into the generated HTML without sanitization, allowing attackers to break out of the intended text context and inject <script> payloads or event-handler attributes.

Attack Vector

Exploitation occurs over the network. An attacker distributes a URL containing a malicious Error value through phishing email, chat, or a compromised web page. When an authenticated online-banking user follows the link, the reflected payload executes in their browser under the banking application's origin. This can be chained with social-engineering pretexts to trigger fraudulent transactions or harvest credentials.

A proof of concept is documented in the GitHub XSS Report Document and cataloged in VulDB #326206.

Detection Methods for CVE-2025-11125

Indicators of Compromise

HTTP GET requests to /connection_error.php containing Error= parameter values with <script>, onerror=, onload=, or javascript: substrings
URL-encoded payloads such as %3Cscript%3E or %3Cimg targeting the Error query parameter
Referer headers pointing to attacker-controlled domains that funnel users to connection_error.php
Anomalous outbound requests from user browsers to external hosts immediately after visiting the banking application

Detection Strategies

Deploy web application firewall rules that inspect the Error parameter on /connection_error.php for HTML and JavaScript metacharacters
Enable server-side request logging with full query string capture and alert on patterns matching known XSS signatures
Perform authenticated dynamic application security testing (DAST) against the Error Message Handler using XSS payload libraries
Review browser Content Security Policy (CSP) violation reports for blocked inline script executions originating from the banking domain

Monitoring Recommendations

Continuously monitor web access logs for the /connection_error.php endpoint and baseline legitimate Error values
Track session anomalies such as concurrent logins from different geographies following a URL click
Correlate email gateway and proxy logs to identify phishing campaigns delivering links to the vulnerable endpoint
Instrument endpoint telemetry to flag browser child processes that receive suspicious command-line arguments after banking sessions

How to Mitigate CVE-2025-11125

Immediate Actions Required

Pull the latest langleyfcu Online Banking System commit and confirm the Error parameter is HTML-encoded before rendering
Deploy a WAF rule that blocks requests to /connection_error.php containing HTML tags or JavaScript event handlers in the Error parameter
Enforce a strict Content Security Policy that disallows inline scripts and restricts script sources to trusted origins
Notify users to avoid clicking unsolicited links referencing the banking domain until the fix is deployed

Patch Information

Because the project uses a rolling release model, no versioned patch identifier is available. Operators should track the upstream repository and apply the commit that introduces context-aware output encoding for the Error parameter in /connection_error.php. Consult the VulDB advisory for remediation guidance.

Workarounds

Apply a reverse-proxy filter that strips or URL-encodes angle brackets and quotes in the Error query parameter before the request reaches the application
Set the HttpOnly and Secure flags on session cookies to reduce the impact of client-side script execution
Configure X-XSS-Protection: 1; mode=block and a restrictive Content-Security-Policy header at the web server layer
Temporarily replace dynamic error output with a static generic error page until the underlying code is patched

bash

# Example NGINX rule to block obvious XSS payloads on the vulnerable endpoint
location = /connection_error.php {
    if ($arg_Error ~* "(<|>|script|onerror|onload|javascript:)") {
        return 403;
    }
    proxy_pass http://backend;
}