A recent vulnerability has been discovered in Jeroen Schmit Theater for WordPress plugin <= .18.3 versions. The vulnerability, identified as CVE-2023-47833, is due to improper neutralization of user input during web page generation. This enables remote attackers to inject arbitrary script code in a user's browser session, resulting in a Cross-site Scripting (XSS) attack. This post discusses the complete details of the vulnerability, potential impact, and mitigation.

CVE ID: CVE-2023-47833

- References: MITRE CVE Page, Official Vendor Security Advisory

Vulnerability Details

The vulnerability lies in the way the Jeroen Schmit Theater plugin filters and neutralizes user-generated input while generating web pages. The lack of proper neutralization allows attackers to inject malicious script code into the user's browser session. As a result, an attacker can potentially steal sensitive data, carry out phishing attacks, or perform various other malicious actions to exploit the user's session.

Proof of Concept (PoC)

To demonstrate this vulnerability, let us consider the following code snipplet from the plugin source code:

// javascript.php
function theather_remove_script_tags($content) {
  return preg_replace('#<script(.*?)>(.*?)</script>#is', '', $content);

This function tries to remove script tags from user-generated content by using a regular expression pattern. However, this implementation is flawed as it allows an attacker to bypass the filter by using fragmented script tags, different cases, or sneaky encodings. For example, the attacker could inject the following payload to bypass the filter:



To exploit this vulnerability, an attacker can create a crafted URL or inject a malicious script into a form input field that will trigger the XSS attack once the victim's browser processes the page. For instance, the attacker could inject the payload mentioned earlier into the comment section of a blog post using the Jeroen Schmit Theater plugin. When a victim visits the page and their browser processes the malicious code, the attacker can potentially execute any arbitrary code within the victim's browser.


The vulnerability has been fixed in the Jeroen Schmit Theater plugin version .18.4. It is strongly recommended that users of the affected plugin versions update to the latest version immediately to address this security issue. Additionally, web application administrators can also apply proper input validation and sanitization mechanisms to prevent such Cross-site Scripting attacks from being successful.


CVE-2023-47833 is a critical vulnerability in the Jeroen Schmit Theater for WordPress plugin that enables remote attackers to perform Cross-site Scripting attacks on users' browser sessions. It is vital to update the plugin to version .18.4 or later to resolve the issue and protect your WordPress website from potential threats. Additionally, implementing robust input validation and sanitization mechanisms can prevent any such vulnerabilities from being exploited in the future.


Published on: 11/23/2023 00:15:08 UTC
Last modified on: 11/28/2023 20:25:42 UTC