CVE-2025-3999: Seeyon OA Web Application System XSS Vulnerability

CVE-2025-3999 Overview

CVE-2025-3999 is a reflected cross-site scripting (XSS) vulnerability [CWE-79] in Seeyon Zhiyuan OA Web Application System 8.1 SP2. The flaw resides in the URL parameter handler of seeyon\opt\Seeyon\A8\ApacheJetspeed\webapps\seeyon\common\js\addDate\date.jsp. Attackers can inject arbitrary script content by manipulating URL parameters processed by this JSP file. The vulnerability is exploitable remotely over the network and requires user interaction with a crafted link. Public disclosure of the exploit technique increases the likelihood of opportunistic abuse against exposed Seeyon OA deployments.

Critical Impact
Successful exploitation allows execution of attacker-controlled JavaScript in the victim's browser session, enabling session theft, phishing overlays, and unauthorized actions within the Seeyon OA portal.

Affected Products

Seeyon Zhiyuan OA Web Application System 8.1 SP2
Component: URL Parameter Handler in date.jsp
File path: seeyon\opt\Seeyon\A8\ApacheJetspeed\webapps\seeyon\common\js\addDate\date.jsp

Discovery Timeline

2025-04-28 - CVE-2025-3999 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-3999

Vulnerability Analysis

The vulnerability exists in date.jsp, a client-side helper that renders date picker components inside the Seeyon OA portal. The JSP reflects one or more URL parameters directly into the response body without applying HTML or JavaScript context encoding. An attacker who crafts a URL containing script payloads can cause the server to echo those payloads back to the victim's browser. Because the rendered content executes within the authenticated session context of the Seeyon OA application, scripts gain access to session cookies, CSRF tokens, and application APIs. The attack requires the victim to click a crafted link, which aligns with the passive user interaction requirement in the CVSS vector.

Root Cause

The root cause is missing output encoding on user-controlled URL parameters inside date.jsp. The JSP concatenates request parameter values into the generated HTML or inline JavaScript without applying context-appropriate escaping. This pattern is the canonical weakness described in [CWE-79], Improper Neutralization of Input During Web Page Generation.

Attack Vector

An unauthenticated or low-privileged attacker crafts a URL targeting the vulnerable date.jsp endpoint with a malicious parameter value. The attacker delivers the link through email, chat, or a watering-hole page. When an authenticated Seeyon OA user visits the link, the reflected payload executes in their browser. Typical post-exploitation actions include stealing JSESSIONID cookies, pivoting to internal OA workflows, and submitting unauthorized requests on behalf of the user. No verified public proof-of-concept code is available, so refer to the VulDB entry #306335 for additional technical context.

Detection Methods for CVE-2025-3999

Indicators of Compromise

HTTP GET requests to /seeyon/common/js/addDate/date.jsp containing URL-encoded <script>, javascript:, onerror=, or onload= substrings.
Web server access logs showing abnormally long or heavily encoded query strings targeting date.jsp.
Referer headers from external, untrusted domains linking users directly to the date.jsp endpoint.
Browser console errors or Content Security Policy violation reports originating from the OA portal.

Detection Strategies

Deploy web application firewall (WAF) signatures that flag reflected XSS patterns in parameters passed to date.jsp.
Correlate authentication events with suspicious outbound requests from user sessions shortly after visiting the OA portal.
Hunt in proxy logs for Seeyon OA URLs containing script tags or event handler keywords in query parameters.

Monitoring Recommendations

Enable verbose access logging on the Apache Jetspeed container hosting Seeyon OA and forward logs to a centralized analytics platform.
Monitor for anomalous session cookie reuse across geographically distinct source IP addresses.
Alert on repeated 200-response hits to date.jsp from a small set of sources, which may indicate payload tuning by an attacker.

How to Mitigate CVE-2025-3999

Immediate Actions Required

Restrict external exposure of the Seeyon OA portal and place it behind a VPN or reverse proxy with WAF inspection.
Deploy WAF rules that block script tags, event handlers, and javascript: schemes in query parameters sent to date.jsp.
Advise users to avoid clicking Seeyon OA links received from untrusted sources and to re-authenticate if suspicious behavior appears.

Patch Information

No vendor advisory or official patch has been published in the referenced sources at the time of writing. Monitor Seeyon vendor channels and the VulDB entry #306335 for remediation updates. Until a fix is available, apply compensating controls at the perimeter and browser layers.

Workarounds

Add a strict Content Security Policy (CSP) header to the Seeyon OA responses to block inline script execution.
Configure the Apache Jetspeed server or fronting reverse proxy to reject requests containing suspicious characters in parameters to date.jsp.
Enforce the HttpOnly and Secure attributes on Seeyon session cookies to limit cookie theft via JavaScript.
If the date picker is not required, remove or restrict access to date.jsp through server configuration.

bash

# Example nginx reverse proxy rule to block common XSS payloads targeting date.jsp
location ~* /seeyon/common/js/addDate/date\.jsp {
    if ($args ~* "(<script|javascript:|onerror=|onload=|%3Cscript)") {
        return 403;
    }
    proxy_pass http://seeyon_backend;
    proxy_set_header X-Content-Type-Options nosniff;
    add_header Content-Security-Policy "default-src 'self'; script-src 'self'";
}