CVE-2026-4852: WordPress Image Source Control XSS Flaw

CVE-2026-4852 Overview

The Image Source Control Lite – Show Image Credits and Captions plugin for WordPress contains a Stored Cross-Site Scripting (XSS) vulnerability in the 'Image Source' attachment field. All versions up to and including 3.9.1 are affected due to insufficient input sanitization and output escaping. This vulnerability allows authenticated attackers with Author-level access or above to inject arbitrary web scripts into pages that execute whenever a user accesses an injected page.

Critical Impact

Authenticated attackers can persistently inject malicious JavaScript that executes in the browsers of all users viewing affected pages, potentially leading to session hijacking, credential theft, or further site compromise.

Affected Products

• Image Source Control Lite – Show Image Credits and Captions plugin for WordPress versions up to and including 3.9.1

Discovery Timeline

• 2026-04-20 - CVE CVE-2026-4852 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-4852

Vulnerability Analysis

This Stored Cross-Site Scripting (XSS) vulnerability (CWE-79) exists within the Image Source Control Lite plugin's handling of the 'Image Source' attachment field. The vulnerability stems from the plugin's failure to properly sanitize user-supplied input before storing it in the database and its inadequate output escaping when rendering the stored content on WordPress pages.

When an authenticated user with Author-level privileges or higher uploads or edits an image attachment, they can input malicious JavaScript code into the 'Image Source' field. Because the plugin does not adequately validate or sanitize this input, the script is stored in the database. Subsequently, when any user views a page where the affected image's source information is displayed, the malicious script executes within their browser context.

The cross-site scripting attack is particularly dangerous because it is persistent (stored), meaning the malicious payload remains in the system and affects all users who view the compromised content. This can lead to widespread impact including session token theft, keylogging, defacement, and phishing attacks targeting site visitors and administrators.

Root Cause

The root cause of this vulnerability is insufficient input sanitization and output escaping in the plugin's handling of the 'Image Source' attachment field. The plugin code, as referenced in the WordPress Plugin Code Reference, fails to properly escape user-controlled data before rendering it in HTML output. This allows attackers to inject script tags or event handlers that bypass the browser's same-origin policy restrictions.

Attack Vector

The attack requires network access and authenticated access with at least Author-level privileges on the WordPress site. An attacker would:

1. Log into the WordPress admin panel with Author or higher credentials
2. Upload or edit an image in the media library
3. Inject malicious JavaScript code into the 'Image Source' field
4. Save the changes, storing the payload in the database
5. When any user visits a page displaying the image credits, the malicious script executes

The vulnerability exploits the trust relationship between the plugin and the stored content. Since no proper output escaping is performed in the global-list.php view file, the injected script is rendered directly into the HTML without sanitization, allowing it to execute in the victim's browser.

Detection Methods for CVE-2026-4852

Indicators of Compromise

• Unexpected JavaScript code or HTML tags present in the 'Image Source' fields of media attachments
• Reports of unusual browser behavior or pop-ups when viewing pages with image credits
• Suspicious network requests originating from pages displaying image source information
• User complaints about redirects or phishing attempts when browsing the site

Detection Strategies

• Review media library entries for suspicious content in the 'Image Source' attachment field containing script tags, event handlers (e.g., onerror, onload), or encoded JavaScript
• Implement Web Application Firewall (WAF) rules to detect XSS payloads in HTTP POST requests to media attachment endpoints
• Use browser-based monitoring tools to detect unexpected script execution on pages displaying image credits

Monitoring Recommendations

• Enable detailed WordPress audit logging to track changes to media attachment metadata
• Monitor server logs for unusual patterns in requests to media library endpoints
• Configure Content Security Policy (CSP) headers to report and potentially block inline script execution
• Regularly scan the database for potentially malicious content stored in attachment metadata fields

How to Mitigate CVE-2026-4852

Immediate Actions Required

• Update the Image Source Control Lite plugin to a version newer than 3.9.1 that addresses this vulnerability
• Review all existing media attachments for suspicious content in the 'Image Source' field and remove any malicious payloads
• Audit user accounts with Author-level access or higher to ensure they are trusted and have not been compromised
• Implement Content Security Policy (CSP) headers to mitigate the impact of any existing XSS payloads

Patch Information

Administrators should check the Wordfence Vulnerability Report for the latest patch information and update the Image Source Control Lite plugin to the most recent version that addresses this vulnerability. Ensure automatic updates are enabled for WordPress plugins where possible.

Workarounds

• Temporarily deactivate the Image Source Control Lite plugin until a patched version is available
• Restrict user roles with Author-level access to trusted personnel only
• Implement a WAF rule to sanitize input to the 'Image Source' attachment field
• Use a security plugin that provides XSS protection and input validation at the WordPress application level

# Example: WordPress CLI command to check plugin version
wp plugin list --name=image-source-control-isc --fields=name,version,status

# Example: Search for potentially malicious content in database (use with caution)
wp db query "SELECT ID, post_title FROM wp_posts WHERE post_type='attachment' AND ID IN (SELECT post_id FROM wp_postmeta WHERE meta_key LIKE '%isc%' AND meta_value LIKE '%<script%')"