Executive Summary

CVE-2025-15093 is a reflected Cross-Site Scripting (XSS) vulnerability in the FlyCMS project, specifically in the Admin Login component's /system/login endpoint. The vulnerability occurs because the redirectUrl parameter is not properly encoded before being included in the web page response. This allows an attacker to inject malicious JavaScript code via the redirectUrl parameter, which is then executed in the context of users visiting the login page. The flaw is located in the IndexAdminController.java file, where the redirectUrl parameter is added directly to the model without encoding. [1, 2, 3]

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Impact Analysis

This vulnerability can allow attackers to execute arbitrary JavaScript code in the context of users visiting the affected login page. This can lead to theft of session cookies, unauthorized actions performed on behalf of users, delivery of malicious payloads, and compromise of data integrity. The attack can be initiated remotely without authentication but requires user interaction. Because the vulnerability is reflected XSS, it can be exploited by tricking users into clicking crafted links. [1, 2, 3]

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Detection Guidance

This vulnerability can be detected by sending a crafted HTTP GET request to the /system/login endpoint with a malicious payload in the redirectUrl parameter and observing if the payload is reflected unencoded in the response, indicating a Reflected Cross-Site Scripting (XSS) vulnerability. For example, using curl or a Python script to send a request like: curl -i 'http://target/system/login?redirectUrl=%22%3E%3CsCriPt%3Ealert(%22zast-xss%22)%3C/scrIpt%3E//' and checking if the response contains the injected script tag unencoded. Alternatively, a Python script using the requests library can automate this test by sending the crafted request and inspecting the response content for the payload. This confirms the presence of the vulnerability. [1]

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Mitigation Strategies

No official mitigation or patch is currently available from the vendor, as they have not responded to the disclosure. Immediate steps include avoiding use of the affected FlyCMS version, restricting access to the /system/login endpoint if possible, and considering alternative products to mitigate risk. Additionally, implementing web application firewall (WAF) rules to detect and block malicious payloads targeting the redirectUrl parameter can help reduce exposure. Monitoring for suspicious activity and educating users about the risk of XSS attacks are also recommended. [2]

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