CVE-2026-1809 in HTML Tag Shortcodes Plugin
Summary
by MITRE • 02/11/2026
The HTML Tag Shortcodes plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's shortcodes in all versions up to, and including, 1.1 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 • 02/12/2026
The HTML Tag Shortcodes plugin for WordPress represents a critical security vulnerability classified as CVE-2026-1809, affecting all versions up to and including 1.1. This vulnerability manifests as a stored cross-site scripting flaw that exploits the plugin's handling of user-supplied shortcode attributes. The weakness stems from inadequate input sanitization mechanisms and insufficient output escaping procedures that fail to properly validate or encode user-provided data before it is stored and subsequently rendered in web pages. Attackers with contributor-level privileges or higher can leverage this vulnerability to inject malicious scripts into the plugin's shortcode processing functionality, creating persistent threats that execute automatically when affected pages are accessed by unsuspecting users.
The technical exploitation of this vulnerability follows a well-established pattern that aligns with CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') and CWE-80 - Improper Neutralization of Script-Related HTML Tags in a Web Page. The flaw occurs because the plugin fails to implement proper sanitization routines for shortcode attributes that are processed through the WordPress shortcode API. When administrators or contributors create or modify content containing shortcodes with malicious attributes, the system stores these inputs without adequate validation. The vulnerability becomes particularly dangerous because it operates as a stored XSS attack rather than a reflected one, meaning the malicious code persists in the database and executes automatically for any user who views the affected content. This characteristic places the vulnerability squarely within the ATT&CK framework under T1059.001 - Command and Scripting Interpreter: PowerShell, as it enables attackers to execute arbitrary code through web-based interfaces.
The operational impact of CVE-2026-1809 extends beyond simple script execution, creating potential pathways for more sophisticated attacks that can compromise entire WordPress installations. An authenticated attacker with contributor privileges can craft malicious shortcodes that, when processed by the vulnerable plugin, could redirect users to malicious domains, steal session cookies, perform unauthorized actions on behalf of users, or even establish persistent backdoors within the WordPress environment. The stored nature of the vulnerability means that the malicious payloads remain active until manually removed from the database, potentially affecting all users who access the compromised pages. This makes the vulnerability particularly concerning for high-traffic WordPress sites where content contributors may have varying levels of security awareness. The attack vector specifically targets the WordPress shortcode processing system, which is commonly used throughout WordPress installations for creating dynamic content, making the exploitation surface area particularly broad.
Mitigation strategies for CVE-2026-1809 should prioritize immediate plugin updates to versions that address the input sanitization and output escaping deficiencies. Organizations should implement strict access controls to limit contributor-level privileges to trusted users only, as the vulnerability requires at least contributor access to exploit effectively. Additionally, administrators should conduct thorough audits of existing content to identify and remove any potentially malicious shortcodes that may have been injected prior to patching. The implementation of web application firewalls and content security policies can provide additional layers of protection by monitoring for suspicious script patterns and preventing execution of unauthorized code. Security monitoring should include regular checks for unauthorized shortcode modifications and user access logs to detect potential exploitation attempts. Organizations should also consider implementing automated vulnerability scanning tools that can identify and alert on stored XSS vulnerabilities in WordPress plugins, particularly those that process user input through shortcode mechanisms. The vulnerability's classification as a stored XSS issue means that traditional browser-based XSS protections may be insufficient, requiring more comprehensive security measures including proper input validation, output encoding, and privilege-based access controls to effectively mitigate the risk.