CVE-2025-26589

Vulnerability

Overview

CVE-2025-26589 is a reflected Cross-Site Scripting (XSS) vulnerability in the WordPress plugin IE CSS3 Support, affecting versions from n/a through 2.0.1. The issue stems from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject arbitrary HTML and JavaScript into the response. This type of flaw is classified as a reflected XSS because the malicious payload is immediately echoed back in the server's response without proper sanitization [1].

Exploitation

Prerequisites

To exploit this vulnerability, an attacker must craft a malicious URL containing the XSS payload and trick a privileged user (such as an administrator) into clicking it. Successful exploitation requires user interaction—the victim must visit the crafted link, which triggers the execution of the injected script in the context of the vulnerable WordPress site. No authentication is needed from the attacker, but the target user must be logged into the site for the attack to succeed [1].

Impact

If exploited, an attacker can execute arbitrary JavaScript in the victim's browser, leading to actions such as redirecting visitors to malicious sites, injecting advertisements, stealing session cookies, or defacing the website. The vulnerability is considered moderately dangerous and is expected to be used in mass-exploit campaigns targeting thousands of WordPress sites regardless of their size or popularity [1].

Mitigation

As of the publication date, no official patch has been released for the IE CSS3 Support plugin. The recommended immediate action is to update the plugin to a patched version if one becomes available. Alternatively, users can apply a mitigation rule provided by Patchstack to block attacks until an official fix can be tested and safely deployed. Site administrators unable to update should consult their hosting provider or web developer for assistance [1].