Description

The Simple Ajax Chat WordPress plugin before 20260827 does not escape chat message content before rendering it, allowing unauthenticated users to inject arbitrary HTML attributes into the page and run scripts in the browser of anyone viewing the chat, including administrators.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-02T06:17:19.773Z",
  "pubdate": "2026-09-02T06:17:19.773Z",
  "executiveSummary": "The Simple Ajax Chat WordPress plugin prior to version 20260827 contains a critical Stored Cross-Site Scripting (XSS) vulnerability. This flaw stems from the failure to properly sanitize or escape user-supplied chat message content before rendering it within the application's DOM.\nThe vulnerability allows unauthenticated attackers to inject arbitrary HTML attributes and malicious JavaScript payloads into chat messages. When a victim, including high-privilege administrators, views the affected chat interface, the injected script executes within the context of their session.\nThe risk implication is severe, as successful exploitation can lead to full account takeover, unauthorized administrative actions, sensitive data exfiltration (such as session cookies or CSRF tokens), and the redirection of users to malicious external domains. Because the injection occurs in a persistent (stored) manner, every user interacting with the chat interface is susceptible to the payload, making this an ideal vector for widespread client-side attacks.\nThere are no specific authentication or privilege requirements for an attacker, as the chat functionality is typically exposed to the public-facing side of the website, enabling anonymous exploitation.",
  "technicalDetails": "The root cause of this vulnerability is an improper implementation of output encoding and input sanitization mechanisms within the Simple Ajax Chat plugin's message rendering logic. The application accepts chat input via an AJAX request and stores the raw text content in the database without performing necessary HTML entity encoding or stripping dangerous tags/attributes.\nWhen the browser renders the chat history, it interprets the stored payload as legitimate HTML elements or attributes. Specifically, the application fails to mitigate the injection of arbitrary HTML attributes, which allows an attacker to break out of the intended HTML structure.\nAttack Flow: 1. An attacker crafts a malicious chat message containing JavaScript payloads embedded within event handlers (e.g., 'onmouseover') or standard script tags. 2. The attacker submits this message via the chat interface, which the server stores in the database without modification. 3. When an authenticated user (e.g., an administrator) loads the page containing the chat box, the server retrieves the malicious string and serves it to the browser as part of the page source. 4. The victim's browser parses the malicious content, triggering the execution of the injected script within the security context of the victim's session.\nThis vulnerability is classified as Stored XSS because the malicious script is persisted on the server, ensuring that it impacts all users who view the chat history. The lack of input sanitization means the plugin does not enforce a 'Content-Security-Policy' (CSP) compliant rendering pipeline or use functions like 'esc_html()' or 'wp_kses_post()' when outputting message data.\nPost-exploitation, an attacker can leverage this execution to perform unauthorized actions on behalf of the victim. If an administrator is the target, the attacker could programmatically create new administrative users, change plugin configurations, or inject secondary malicious backdoors into the WordPress theme or plugin files. Furthermore, because the script runs in the browser, the attacker can silently harvest sensitive cookies (if not marked HttpOnly), perform authenticated requests through the victim's session, or conduct further client-side reconnaissance."
}