CVE-2026-30564: Sales And Inventory System XSS Flaw

CVE-2026-30564 Overview

A Reflected Cross-Site Scripting (XSS) vulnerability exists in SourceCodester Sales and Inventory System 1.0. The vulnerability is located in the view_payments.php file via the limit parameter. The application fails to sanitize the input, allowing remote attackers to inject arbitrary web script or HTML via a crafted URL.

Critical Impact

Attackers can execute arbitrary JavaScript code in the context of a victim's browser session, potentially leading to session hijacking, credential theft, or malicious actions performed on behalf of authenticated users.

Affected Products

• SourceCodester Sales and Inventory System 1.0
• ahsanriaz26gmailcom:sales_and_inventory_system (cpe:2.3:a:ahsanriaz26gmailcom:sales_and_inventory_system:1.0:::::::*)

Discovery Timeline

• 2026-03-30 - CVE CVE-2026-30564 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2026-30564

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Reflected Cross-Site Scripting. The vulnerable component is the view_payments.php file within the Sales and Inventory System application, which processes user input through the limit parameter without proper sanitization or encoding.

When a user clicks on a crafted malicious URL containing JavaScript code in the limit parameter, the server reflects this unsanitized input back to the user's browser, which then executes the injected script in the context of the vulnerable web application. This attack requires user interaction, as the victim must click on or otherwise access the malicious URL.

The attack can be executed remotely over the network without requiring authentication or special privileges. However, the impact is limited to confidentiality and integrity breaches within the scope of the victim's session, with no direct availability impact on the underlying system.

Root Cause

The root cause of this vulnerability is the failure to properly sanitize, validate, or encode user-controlled input in the limit parameter before reflecting it in the HTTP response. The view_payments.php script directly incorporates the limit parameter value into the HTML output without implementing output encoding (such as HTML entity encoding) or input validation to strip potentially malicious content.

Attack Vector

The attack is network-based and requires an attacker to craft a malicious URL containing JavaScript payload in the limit parameter. The attacker then needs to social engineer a victim into clicking the link. When the victim visits the crafted URL while authenticated to the Sales and Inventory System, the malicious script executes in their browser session.

Typical exploitation scenarios include:

• Session cookie theft to hijack authenticated user sessions
• Keylogging to capture credentials or sensitive data
• Phishing attacks by injecting fake login forms
• Defacement or modification of page content
• Redirecting users to malicious external sites

For detailed technical information and proof-of-concept, see the GitHub XSS Proof of Concept.

Detection Methods for CVE-2026-30564

Indicators of Compromise

• Review web server access logs for unusual requests to view_payments.php containing suspicious characters in the limit parameter such as <script>, javascript:, onerror=, or encoded variants
• Monitor for URL-encoded or double-encoded payloads targeting the limit parameter
• Look for Base64-encoded strings or other obfuscation techniques in HTTP request parameters
• Check for cookie exfiltration attempts in outbound network traffic following visits to the application

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block common XSS patterns in request parameters
• Deploy browser-based Content Security Policy (CSP) headers to restrict execution of inline scripts
• Enable real-time monitoring for JavaScript injection patterns in HTTP traffic
• Utilize SIEM correlation rules to identify suspicious parameter manipulation attempts against the Sales and Inventory System

Monitoring Recommendations

• Enable verbose logging for the view_payments.php endpoint to capture all parameter values
• Configure alerts for requests containing HTML tags or JavaScript event handlers in query strings
• Monitor for unusual outbound connections from client browsers after accessing the application
• Implement honeypot parameters to detect automated scanning attempts

How to Mitigate CVE-2026-30564

Immediate Actions Required

• Restrict access to the Sales and Inventory System to trusted networks or users until a patch is applied
• Implement server-side input validation to whitelist acceptable values for the limit parameter (e.g., numeric values only)
• Apply output encoding (HTML entity encoding) to all user-controlled data before rendering in HTML responses
• Deploy a Web Application Firewall (WAF) with XSS protection rules as an interim measure

Patch Information

No official vendor patch has been announced for this vulnerability at the time of publication. Users of SourceCodester Sales and Inventory System 1.0 should contact the vendor for remediation guidance or apply manual fixes to the vulnerable view_payments.php file.

For technical details about the vulnerability, refer to the GitHub XSS Proof of Concept.

Workarounds

• Implement Content Security Policy (CSP) headers to prevent inline script execution: Content-Security-Policy: default-src 'self'; script-src 'self'
• Add server-side input validation to ensure the limit parameter only accepts numeric values
• Apply PHP htmlspecialchars() or equivalent output encoding functions to sanitize reflected input
• Consider placing the application behind an authenticated reverse proxy to limit exposure

# Example Apache configuration to add CSP headers
<IfModule mod_headers.c>
    Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'"
    Header set X-XSS-Protection "1; mode=block"
    Header set X-Content-Type-Options "nosniff"
</IfModule>