CVE-2026-57745: RT-Theme 18 Extensions XSS Vulnerability

CVE-2026-57745 Overview

CVE-2026-57745 is a reflected Cross-Site Scripting (XSS) vulnerability in the stmcan RT-Theme 18 | Extensions (rt18-extensions) WordPress plugin. The flaw affects all plugin versions up to and including 2.5. Attackers exploit the issue by crafting malicious URLs that inject unescaped input into rendered web pages. Successful exploitation requires user interaction, such as clicking a specially crafted link. The vulnerability is classified under CWE-79 — Improper Neutralization of Input During Web Page Generation.

Critical Impact
Attackers can execute arbitrary JavaScript in a victim's browser session, enabling session hijacking, credential theft, and redirection to attacker-controlled infrastructure.

Affected Products

stmcan RT-Theme 18 | Extensions (rt18-extensions) plugin
All versions from n/a through <= 2.5
WordPress sites using the RT-Theme 18 Extensions plugin

Discovery Timeline

2026-07-13 - CVE-2026-57745 published to NVD
2026-07-13 - Last updated in NVD database

Technical Details for CVE-2026-57745

Vulnerability Analysis

The vulnerability stems from improper neutralization of user-supplied input in the rt18-extensions plugin. The plugin reflects request parameters into HTTP responses without applying context-appropriate output encoding. When a victim loads a crafted URL, the browser parses attacker-controlled markup as part of the trusted origin.

Reflected XSS operates within the victim's authenticated session. If an administrator clicks the malicious link, attackers can perform actions with elevated WordPress privileges. Injected scripts can read cookies not marked HttpOnly, exfiltrate nonces, or issue authenticated requests to WordPress REST endpoints.

The scope change (S:C) in the CVSS vector indicates the injected payload can affect resources beyond the vulnerable component, such as other browser origins or session tokens shared across the WordPress admin surface.

Root Cause

The plugin fails to sanitize input using WordPress helpers such as esc_html(), esc_attr(), or wp_kses() before echoing values into the response body. Input received through query parameters flows directly into HTML output. This missing output encoding is the canonical pattern captured by CWE-79.

Attack Vector

An unauthenticated remote attacker crafts a URL containing a JavaScript payload in a vulnerable parameter handled by rt18-extensions. The attacker distributes the link through phishing email, social media, or a compromised site. When a logged-in WordPress user visits the URL, the payload executes in the browser under the site's origin.

The vulnerability manifests when unsanitized request data is reflected into the response. Refer to the Patchstack Vulnerability Report for technical details.

Detection Methods for CVE-2026-57745

Indicators of Compromise

HTTP requests to rt18-extensions endpoints containing URL-encoded <script>, onerror=, javascript:, or onload= payloads in query parameters
Web server access logs showing long, obfuscated query strings targeting plugin pages
Referrer headers pointing to unfamiliar external domains preceding administrative actions
Unexpected outbound requests from admin browsers to attacker-controlled domains shortly after clicking inbound links

Detection Strategies

Deploy a Web Application Firewall (WAF) rule set to flag reflected XSS signatures on requests to /wp-content/plugins/rt18-extensions/ paths
Correlate WordPress wp-login.php and REST API activity with recent query strings containing HTML control characters
Review browser Content Security Policy (CSP) violation reports for inline script blocks originating from plugin URLs

Monitoring Recommendations

Enable verbose HTTP request logging on the WordPress reverse proxy or web server
Monitor administrator session anomalies such as unexpected privilege changes, new user creation, or plugin installation events
Alert on cookie theft indicators, including sessions used from geographies inconsistent with the assigned user

How to Mitigate CVE-2026-57745

Immediate Actions Required

Update the rt18-extensions plugin to a patched release once published by the vendor
Audit WordPress administrator accounts and rotate credentials and session tokens if suspicious activity is present
Restrict /wp-admin/ access by IP allowlist where operationally feasible
Enforce multi-factor authentication for all privileged WordPress accounts

Patch Information

At publication, the Patchstack Vulnerability Report lists versions up to and including 2.5 as affected. Administrators should monitor the vendor advisory for a fixed release and apply it promptly. Until a patch is available, treat the plugin as vulnerable and apply compensating controls.

Workarounds

Deactivate the rt18-extensions plugin until a fixed version is available if the functionality is non-essential
Deploy WAF rules that block requests containing script tags, event handlers, or javascript: URIs targeting plugin endpoints
Configure a strict Content Security Policy header that disallows inline scripts and restricts script sources to trusted origins
Instruct administrators to avoid clicking unsolicited links pointing to the WordPress site while authenticated

bash

# Example nginx rule to block common reflected XSS payloads targeting the plugin
location ~* /wp-content/plugins/rt18-extensions/ {
    if ($args ~* "(<|%3C)script|onerror=|onload=|javascript:") {
        return 403;
    }
}