CVE-2025-4599: Liferay DXP postMessage-based XSS Vulnerability

CVE-2025-4599 Overview

CVE-2025-4599 is a cross-site scripting (XSS) vulnerability [CWE-79] in the fragment preview functionality of Liferay Portal and Liferay Digital Experience Platform (DXP). The flaw allows a remote unauthenticated attacker to inject JavaScript into the fragment portlet URL through a postMessage-based vector. When a user visits a crafted preview URL, the injected script executes in the browser context of the Liferay application.

Critical Impact
Attackers can execute arbitrary JavaScript in the context of a victim's browser session, enabling session theft, phishing, and unauthorized actions against Liferay Portal instances.

Affected Products

Liferay Portal 7.4.3.61 through 7.4.3.132
Liferay DXP 2024.Q1.1 – 2024.Q1.13, 2024.Q2.0 – 2024.Q2.13, 2024.Q3.1 – 2024.Q3.13, 2024.Q4.1 – 2024.Q4.5
Liferay DXP 7.4 update 61 through update 92

Discovery Timeline

2025-08-04 - CVE-2025-4599 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-4599

Vulnerability Analysis

The vulnerability resides in Liferay's fragment preview functionality, which renders draft fragments in an iframe and communicates with the parent window using the browser postMessage API. The parent handler consumes message data and reflects attacker-controlled values into the fragment portlet URL without adequate sanitization or origin validation. This allows script payloads to reach a JavaScript execution sink.

Because the attack requires no authentication, an adversary can host a malicious page that opens or embeds the Liferay preview endpoint and posts a crafted message. The injected script executes in the Liferay origin, giving the attacker access to session cookies not marked HttpOnly, CSRF tokens rendered in the DOM, and any authenticated user actions available in the current session.

Root Cause

The root cause is missing output encoding and insufficient validation of message payloads received via window.postMessage. The preview logic trusts inbound messages and inserts values into a URL that is subsequently used to construct DOM content or navigation, satisfying the classic reflected XSS pattern described in [CWE-79].

Attack Vector

The attack requires user interaction. A victim must load an attacker-controlled page or click a crafted link while a Liferay instance is reachable. The malicious page then invokes postMessage against the Liferay preview window, delivering a JavaScript payload embedded in the fragment portlet URL. No credentials or prior privileges on the target Liferay instance are required by the attacker, though the impact is realized in the victim's browser session.

See the Liferay Security Advisory CVE-2025-4599 for vendor technical details. No public proof-of-concept or exploit code has been released.

Detection Methods for CVE-2025-4599

Indicators of Compromise

Requests to fragment preview endpoints containing URL-encoded <script>, javascript:, or onerror= payloads in query parameters.
Unusual Referer headers pointing to external domains that load Liferay preview URLs in iframes.
Anomalous outbound requests from authenticated Liferay user sessions to attacker-controlled hosts shortly after preview access.

Detection Strategies

Inspect web server and reverse proxy logs for fragment portlet URLs containing script-like tokens or encoded HTML entities in parameters.
Deploy a web application firewall (WAF) rule set that flags reflected XSS patterns targeting Liferay preview and portlet paths.
Correlate browser-side Content Security Policy (CSP) violation reports with Liferay origins to surface script injection attempts.

Monitoring Recommendations

Alert on authenticated Liferay sessions that exhibit rapid privilege-sensitive actions immediately following preview page access.
Monitor for external domains embedding Liferay URLs via iframe by reviewing HTTP Sec-Fetch-Site and Origin headers at the edge.
Track administrator account activity for unexpected content changes that could indicate a hijacked session.

How to Mitigate CVE-2025-4599

Immediate Actions Required

Upgrade Liferay Portal to a version beyond 7.4.3.132 and Liferay DXP to the latest fixed quarterly release as documented in the vendor advisory.
Apply the corresponding DXP update for 7.4 update 92 or later on self-hosted instances.
Restrict administrative access to the fragment preview functionality to trusted networks until patching is complete.

Patch Information

Liferay has published fix guidance in the Liferay Security Advisory CVE-2025-4599. Customers on Liferay DXP subscriptions should apply the latest quarterly release update. Community users of Liferay Portal should upgrade to a release later than 7.4.3.132.

Workarounds

Enforce a strict Content Security Policy that disallows inline script execution and restricts script sources to the Liferay origin.
Configure the reverse proxy to reject fragment preview requests containing HTML metacharacters in query parameters.
Set session cookies with HttpOnly and SameSite=Strict attributes to limit the impact of script execution against authenticated users.

bash

# Example nginx snippet enforcing CSP and blocking suspicious preview parameters
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; frame-ancestors 'self'" always;

location ~* /o/fragment/preview {
    if ($args ~* "(<|%3C)script|javascript:|onerror=") {
        return 403;
    }
}