CVE-2025-41081: IsMyGym Reflected XSS Vulnerability

CVE-2025-41081 Overview

A Reflected Cross-Site Scripting (XSS) vulnerability has been identified in IsMyGym, a gym management application developed by Zuinq Studio. This vulnerability allows an attacker to execute arbitrary JavaScript code in a victim's browser by crafting a malicious URL containing XSS payloads in the path component using the pattern /<PATH>.php/<XSS>.

When a user clicks on a specially crafted malicious link, the attacker's JavaScript code executes within the context of the vulnerable application. This can be exploited to steal sensitive user data, including session cookies, or to perform unauthorized actions on behalf of the authenticated user.

Critical Impact

Attackers can steal session cookies and user credentials, perform actions as authenticated users, redirect victims to malicious websites, or deface the application interface through client-side script injection.

Affected Products

• IsMyGym by Zuinq Studio (specific versions not disclosed)

Discovery Timeline

• 2026-01-20 - CVE-2025-41081 published to NVD
• 2026-01-20 - Last updated in NVD database

Technical Details for CVE-2025-41081

Vulnerability Analysis

The reflected XSS vulnerability in IsMyGym stems from insufficient input validation and output encoding in the application's PHP files. When user-controlled input is passed through the URL path and subsequently reflected in the HTTP response without proper sanitization, the application fails to neutralize potentially malicious script content.

This vulnerability follows the classic reflected XSS pattern where the attack payload is delivered via a URL parameter or path segment and is immediately reflected back in the server's response. Since the malicious script executes in the victim's browser session, it has access to the same privileges and data as the legitimate user, including session tokens, cookies, and the ability to make authenticated requests.

Root Cause

The root cause of this vulnerability is improper input validation and lack of output encoding in the IsMyGym application. PHP scripts in the application accept user-supplied input through the URL path structure (/<PATH>.php/<XSS>) and reflect this input back in the HTML response without proper sanitization or encoding. This allows attackers to inject arbitrary HTML and JavaScript code that gets executed in the victim's browser context.

Attack Vector

The attack is network-based and requires user interaction to be successful. An attacker must craft a malicious URL containing the XSS payload and convince a victim to click on it through social engineering techniques such as phishing emails, malicious links on forums, or embedded links in third-party websites.

The attack chain typically follows this pattern:

1. The attacker identifies a vulnerable PHP endpoint in the IsMyGym application
2. A malicious URL is crafted with JavaScript payload embedded in the path component
3. The victim is tricked into clicking the malicious link via social engineering
4. When the victim's browser requests the malicious URL, the server reflects the unencoded payload in the response
5. The victim's browser executes the attacker's JavaScript code within the application's security context

Since this is a reflected XSS vulnerability, the malicious payload is delivered through the URL path rather than being stored on the server. The attack exploits the application's failure to properly encode output when rendering user-supplied path information in the response. For detailed technical information, refer to the INCIBE Security Notice.

Detection Methods for CVE-2025-41081

Indicators of Compromise

• Unusual URL patterns containing encoded JavaScript or HTML tags in the path component (e.g., <script>, onerror=, javascript:)
• HTTP requests to PHP endpoints with suspicious path segments containing special characters like <, >, ", ', or encoded equivalents (%3C, %3E)
• Browser-side warnings or Content Security Policy (CSP) violations indicating script injection attempts
• User reports of unexpected browser behavior or suspicious redirects when accessing IsMyGym URLs

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block requests containing common XSS payloads in URL paths
• Enable application logging to capture all incoming requests and monitor for patterns consistent with XSS attack attempts
• Deploy Content Security Policy (CSP) headers with report-uri or report-to directives to receive alerts when script injection attempts are blocked
• Use intrusion detection systems (IDS) to identify network traffic patterns associated with XSS exploitation

Monitoring Recommendations

• Monitor web server access logs for requests with URL-encoded JavaScript or HTML injection patterns
• Review authentication logs for suspicious session activity that may indicate session cookie theft
• Implement real-time alerting for CSP violation reports to detect active exploitation attempts
• Correlate unusual user account activity with web traffic logs to identify potential session hijacking

How to Mitigate CVE-2025-41081

Immediate Actions Required

• Contact Zuinq Studio to inquire about available security patches or updates for IsMyGym
• Implement a Web Application Firewall (WAF) to filter malicious requests containing XSS payloads
• Deploy Content Security Policy (CSP) headers to restrict script execution sources
• Educate users about the risks of clicking on untrusted links, especially those pointing to the IsMyGym application

Patch Information

No specific patch information is available at this time. Organizations using IsMyGym should contact Zuinq Studio directly for remediation guidance. Monitor the INCIBE Security Notice for updates on available fixes.

Workarounds

• Configure a Web Application Firewall (WAF) with rules to detect and block common XSS patterns in URL paths
• Implement strict Content Security Policy (CSP) headers to prevent inline script execution: script-src 'self'
• Add HTTP response headers such as X-XSS-Protection: 1; mode=block and X-Content-Type-Options: nosniff for additional browser-level protections
• Restrict access to the IsMyGym application to trusted network segments or implement additional authentication layers

# Apache .htaccess CSP configuration example
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:;"
Header set X-XSS-Protection "1; mode=block"
Header set X-Content-Type-Options "nosniff"
Header set X-Frame-Options "SAMEORIGIN"