CVE-2026-1820 in Media Library Alt Text Editor Plugin
Summary
by MITRE • 03/07/2026
The Media Library Alt Text Editor plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's 'bvmalt_sc_div_update_alt_text' shortcode in all versions up to, and including, 1.0.0 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
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Analysis
by VulDB Data Team • 03/08/2026
The Media Library Alt Text Editor plugin for WordPress presents a critical stored cross-site scripting vulnerability identified as CVE-2026-1820 affecting all versions through 1.0.0. This vulnerability stems from inadequate input sanitization and output escaping mechanisms within the plugin's core functionality, specifically within the 'bvmalt_sc_div_update_alt_text' shortcode implementation. The flaw exists at the intersection of web application security principles and content management system vulnerabilities, creating a persistent threat vector that can compromise user sessions and execute malicious code within the context of affected websites.
The technical exploitation of this vulnerability occurs through the manipulation of user-supplied attributes within the shortcode parameter structure. Attackers with contributor-level privileges or higher can inject malicious scripts into the alt text fields that are subsequently stored within the WordPress database. When other users access pages containing these compromised alt text elements, the stored scripts execute automatically in their browsers, creating a persistent XSS attack vector. This represents a classic stored XSS vulnerability classified under CWE-79, which specifically addresses improper neutralization of input during web page generation in web applications.
The operational impact of this vulnerability extends beyond simple script execution, as it enables attackers to perform session hijacking, defacement of content, and potentially escalate privileges within the WordPress environment. The vulnerability affects the integrity of the content management system by allowing unauthorized modification of data that appears to be legitimate user-generated content. This threat is particularly concerning in multi-user WordPress environments where contributors and authors may have varying levels of trust, as the attack can propagate through the system without requiring elevated privileges beyond contributor access. The attack vector aligns with ATT&CK technique T1566.001 for credential access through spearphishing attachments and T1059.001 for command and control through scripting.
Mitigation strategies for this vulnerability require immediate attention from WordPress administrators and security teams. The primary solution involves updating to the latest version of the Media Library Alt Text Editor plugin where the XSS vulnerability has been addressed through proper input sanitization and output escaping mechanisms. Organizations should implement comprehensive input validation procedures that sanitize all user-supplied data before storage and ensure that all output is properly escaped according to the context in which it is rendered. Additionally, implementing content security policies and restricting contributor-level permissions to minimize potential attack surface areas can provide layered defense against similar vulnerabilities. The vulnerability demonstrates the critical importance of proper input validation and output escaping in preventing XSS attacks, reinforcing principles outlined in the OWASP Top Ten and the Web Application Security Consortium guidelines for secure web application development.