CVE-2025-40734: Daily Expense Manager XSS Vulnerability

CVE-2025-40734 Overview

CVE-2025-40734 is a Reflected Cross-Site Scripting (XSS) vulnerability affecting Code-projects Daily Expense Manager version 1.0. The flaw resides in the /register.php endpoint, where the password and confirm_password parameters submitted through a POST request are reflected back to the user without proper sanitization. An attacker can craft malicious input containing JavaScript that executes in the victim's browser session when the response is rendered. The vulnerability is tracked under CWE-79: Improper Neutralization of Input During Web Page Generation. Exploitation requires user interaction, typically achieved through phishing links or maliciously crafted pages that trigger the vulnerable request.

Critical Impact
Successful exploitation allows attackers to execute arbitrary JavaScript in a victim's browser, enabling session manipulation, credential theft during registration, and delivery of secondary payloads.

Affected Products

Code-projects Daily Expense Manager 1.0
/register.php endpoint with password parameter
/register.php endpoint with confirm_password parameter

Discovery Timeline

2025-06-30 - CVE-2025-40734 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-40734

Vulnerability Analysis

The vulnerability is a Reflected Cross-Site Scripting flaw in the registration workflow of Daily Expense Manager v1.0. When a user submits the registration form, values from the password and confirm_password POST parameters are echoed back into the HTML response without output encoding or input filtering. This behavior allows attacker-controlled JavaScript payloads to render as executable script within the response page.

Because the injection point is inside a form submission response, an attacker must convince a victim to submit a crafted POST request to /register.php. This is typically achieved by hosting a malicious auto-submitting form on an attacker-controlled site or embedding one inside a phishing page. The EPSS score of 0.183% reflects a low probability of observed exploitation, consistent with the small deployment footprint of this application.

Root Cause

The root cause is missing output encoding on user-supplied form data. The /register.php handler concatenates the submitted password and confirm_password values directly into HTML output, likely as part of validation feedback or form re-population. No context-aware escaping (such as HTML entity encoding) is applied before rendering.

Attack Vector

Exploitation occurs over the network and requires user interaction. An attacker crafts a POST request targeting /register.php with a JavaScript payload placed in the password or confirm_password field. When the victim submits this request, the server reflects the payload into the response HTML, causing the browser to execute the injected script under the origin of the vulnerable application. The impact is limited to the browser session and any subsystem the injected script can reach.

Because realCodeExamples are not available for this CVE, refer to the INCIBE Security Notice for additional technical detail on the reflection behavior.

Detection Methods for CVE-2025-40734

Indicators of Compromise

POST requests to /register.php containing HTML tags, <script>, onerror=, onload=, or javascript: sequences in the password or confirm_password fields.
HTTP responses from /register.php echoing unescaped angle brackets or event handler attributes back to the client.
Referrer headers on registration requests pointing to external, unaffiliated domains hosting auto-submitting forms.

Detection Strategies

Deploy web application firewall (WAF) rules that inspect POST bodies to /register.php for XSS payload patterns and block requests containing script tags or JavaScript event handlers in password fields.
Enable web server access logging with request body capture on registration endpoints and correlate suspicious payloads against known XSS signatures.
Perform dynamic application security testing (DAST) against the registration form to confirm reflection behavior and validate detection coverage.

Monitoring Recommendations

Alert on outbound browser requests to unexpected domains originating from sessions that recently interacted with /register.php.
Monitor Content Security Policy (CSP) violation reports from the application origin to identify inline script execution attempts.
Track anomalous spikes in registration endpoint traffic that may indicate mass exploitation attempts through phishing campaigns.

How to Mitigate CVE-2025-40734

Immediate Actions Required

Restrict public access to the Daily Expense Manager v1.0 registration page until the vulnerability is remediated.
Deploy WAF rules that block XSS payload patterns in POST requests targeting /register.php.
Implement a strict Content Security Policy that disallows inline scripts and restricts script sources to trusted origins.

Patch Information

No vendor patch is currently referenced in the enriched CVE data or the INCIBE Security Notice. Organizations should apply input validation and output encoding directly in the affected source or consider discontinuing use of Daily Expense Manager v1.0 until a fixed version is released.

Workarounds

Modify /register.php to apply context-aware HTML entity encoding (for example, htmlspecialchars($input, ENT_QUOTES, 'UTF-8')) on the password and confirm_password values before including them in any HTML response.
Add server-side input validation that rejects registration submissions containing HTML control characters such as <, >, ", and '.
Configure the HttpOnly and Secure flags on session cookies to limit the impact of script execution against authenticated users.

bash

# Example WAF rule (ModSecurity) blocking XSS payloads on the registration endpoint
SecRule REQUEST_URI "@streq /register.php" \
    "phase:2,chain,deny,status:403,id:1004073,\
     msg:'Potential XSS in Daily Expense Manager registration'"
    SecRule ARGS:password|ARGS:confirm_password "@rx (?i)(<script|onerror=|onload=|javascript:)" \
        "t:none,t:urlDecodeUni"