CVE-2025-22635: Imithemes Eventer XSS Vulnerability

CVE-2025-22635 Overview

CVE-2025-22635 is a reflected cross-site scripting (XSS) vulnerability in the imithemes Eventer WordPress plugin, a widely used event booking manager. The flaw stems from improper neutralization of user-supplied input during web page generation [CWE-79]. Attackers can craft a malicious link that, when clicked by an authenticated or unauthenticated visitor, executes arbitrary JavaScript in the victim's browser session. The vulnerability affects all Eventer versions up to and including 3.9.9. Successful exploitation requires user interaction and can lead to session theft, credential harvesting, or unauthorized administrative actions on the affected WordPress site.

Critical Impact
A reflected XSS payload delivered via a crafted URL executes attacker-controlled JavaScript in the victim's browser, enabling session hijacking and defacement on WordPress sites running vulnerable versions of the Eventer plugin.

Affected Products

imithemes Eventer WordPress plugin
All versions from n/a through 3.9.9
WordPress installations using Eventer Event Booking Manager

Discovery Timeline

2025-02-23 - CVE-2025-22635 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-22635

Vulnerability Analysis

CVE-2025-22635 is a reflected cross-site scripting vulnerability in the Eventer plugin for WordPress. The plugin reflects user-supplied request parameters into HTTP responses without proper encoding or sanitization. When a victim visits a specially crafted URL, the injected script executes in the security context of the WordPress site.

Because the injected payload runs in the victim's browser, the attacker can read session cookies not marked HttpOnly, manipulate the DOM, submit forged requests to WordPress administrative endpoints, or redirect users to phishing pages. If an authenticated administrator triggers the payload, the attacker can escalate to persistent site compromise through plugin installation or user creation.

The scope-changed nature of the vulnerability means the impact can extend beyond the vulnerable component to affect the entire WordPress site and its authenticated users. Exploitation requires social engineering to induce a victim to click a crafted link, but no authentication is required on the attacker's side.

Root Cause

The root cause is missing output encoding of request parameters before they are echoed into HTML responses [CWE-79]. The plugin fails to apply WordPress sanitization functions such as esc_html(), esc_attr(), or wp_kses() to values reflected from $_GET or $_POST inputs. This allows attacker-controlled markup and script tags to be rendered as active content.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker constructs a URL to a vulnerable Eventer plugin endpoint with a JavaScript payload embedded in a reflected parameter. The attacker distributes the link via email, social media, or malicious advertising. When a WordPress user visits the URL, the payload executes in their browser. The vulnerability manifests in Eventer request handlers that echo query parameters into search result pages, form fields, or error messages. See the Patchstack WordPress Vulnerability Report for advisory details.

Detection Methods for CVE-2025-22635

Indicators of Compromise

Web server access logs containing requests to Eventer plugin endpoints with URL-encoded <script>, javascript:, onerror=, or onload= payloads in query strings
Unexpected outbound HTTP requests from user browsers to attacker-controlled domains referenced in reflected parameters
Anomalous WordPress administrative actions originating from legitimate admin sessions shortly after link clicks

Detection Strategies

Deploy a web application firewall rule that inspects query strings and POST bodies for XSS signatures targeting the /wp-content/plugins/eventer/ path
Review WordPress access logs for HTTP requests containing suspicious characters such as <, >, %3C, %3E, or javascript: directed at Eventer endpoints
Monitor Content Security Policy (CSP) violation reports for inline script executions on pages served by the plugin

Monitoring Recommendations

Enable verbose WordPress and web server logging for all requests to plugin routes, retaining logs for forensic review
Alert on repeated 200 OK responses to requests carrying encoded script payloads in reflected parameters
Track administrator session activity for anomalies such as unexpected plugin installs, user creation, or option changes following external link visits

How to Mitigate CVE-2025-22635

Immediate Actions Required

Update the imithemes Eventer plugin to a version later than 3.9.9 as soon as a patched release is available from the vendor
If no patch is available, deactivate and remove the Eventer plugin until a fix is released
Force logout of all WordPress administrator sessions and rotate credentials if suspicious activity is observed
Audit WordPress user accounts and installed plugins for unauthorized changes

Patch Information

At the time of publication, the advisory indicates the issue affects Eventer through version 3.9.9. Site administrators should consult the Patchstack advisory and the imithemes vendor portal for the latest fixed release and apply it through the WordPress plugin update mechanism.

Workarounds

Deploy a web application firewall with OWASP Core Rule Set (CRS) XSS rules enabled to filter malicious request parameters
Implement a strict Content Security Policy that disallows inline scripts and restricts script sources to trusted origins
Set the HttpOnly and SameSite=Strict flags on WordPress session cookies to limit the impact of successful XSS
Train administrative users to avoid clicking untrusted links pointing to the WordPress site

bash

# Example nginx configuration adding Content-Security-Policy and cookie hardening
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; frame-ancestors 'none'" always;
add_header X-XSS-Protection "1; mode=block" always;
add_header X-Content-Type-Options "nosniff" always;
proxy_cookie_path / "/; HttpOnly; Secure; SameSite=Strict";