CVE-2026-109998 in Mang Board Plugin
Summary
by MITRE • 10/16/2026
The Mang Board plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'content' parameter in all versions up to, and including, 2.4.3 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This is exploitable because the wp_ajax_nopriv_mb_template endpoint is publicly accessible without authentication, nonce verification is not enforced for the content_reply mode, and admin-ajax.php responds with Content-Type: text/html, causing browsers to execute injected tags embedded in the JSON response body.
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Analysis
by VulDB Data Team • 10/16/2026
The Mang Board plugin for WordPress contains a critical stored cross-site scripting vulnerability affecting all versions up to 2.4.3. This flaw stems from insufficient input sanitization and output escaping mechanisms within the application code, allowing malicious actors to inject arbitrary web scripts into database-stored content. The security failure is specifically located in the handling of the 'content' parameter during template processing operations. Because the vulnerability results in data being stored on the target server rather than merely reflected in a single request, it classifies as a persistent threat that can impact multiple users over an extended period without requiring further interaction from the attacker after the initial injection.
The exploitability of this vulnerability is significantly amplified by architectural weaknesses in how the plugin handles AJAX requests. The endpoint wp_ajax_nopriv_mb_template is publicly accessible and does not require authentication, which allows unauthenticated attackers to interact with it directly. Furthermore, nonce verification is not enforced for the content_reply mode within this specific operation path. This lack of state validation means that any external actor can craft valid-looking requests without possessing a legitimate session token or CSRF protection mechanism typically provided by WordPress core functions.
A critical technical factor enabling successful exploitation is the response handling behavior of admin-ajax.php when processing these malicious payloads. The server responds with a Content-Type header set to text/html rather than application/json, even though the payload may be embedded within what appears to be a JSON structure in the body. Browsers interpreting this response will parse and execute any HTML tags or script elements found within the content field of the response body. This deviation from standard secure practices allows injected JavaScript code to run directly in the context of the victim's browser session, bypassing same-origin policy protections that might otherwise mitigate reflected XSS attacks.
The operational impact of this vulnerability is severe, as it enables unauthenticated attackers to execute arbitrary client-side scripts on behalf of any user who views an affected page or receives a response containing the injected payload. Successful exploitation can lead to complete compromise of user accounts through session hijacking, theft of sensitive administrative credentials stored in browser memory, redirection to malicious phishing sites, and defacement of the website interface. Since the script is stored server-side, it persists across multiple sessions, potentially affecting every visitor who loads the compromised content until the malicious data is manually removed from the database or the plugin is updated.
To mitigate this risk, immediate action should be taken by upgrading the Mang Board plugin to version 2.4.4 or later where these input validation and output encoding issues have been addressed. Administrators must ensure that all WordPress plugins are kept up to date with security patches released by their vendors. In environments where updating is not immediately feasible, implementing a Web Application Firewall can help filter out malicious payloads targeting the wp_ajax_nopriv_mb_template endpoint before they reach the application logic. Additionally, enforcing strict Content Security Policy headers and ensuring proper JSON content type responses for AJAX endpoints can reduce the impact of similar vulnerabilities in other components of the web stack.