CVE-2026-66643 in Shortcode Plugin
Summary
by MITRE • 08/18/2026
Contributor Cross Site Scripting (XSS) in Wufoo Shortcode <= 1.55 versions.
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Analysis
by VulDB Data Team • 08/18/2026
The vulnerability identified as Contributor Cross-Site Scripting within the Wufoo Shortcode plugin, affecting versions up to and including 1.55, represents a significant security flaw rooted in insufficient input validation and output encoding mechanisms. This specific weakness allows attackers with contributor-level or lower privileges on a WordPress installation to inject malicious client-side scripts into web pages viewed by other users. The core of the issue lies in how the plugin processes user-supplied data intended for embedding Wufoo forms via shortcodes, failing to properly sanitize inputs before rendering them within the HTML context. This lack of sanitization creates an entry point where untrusted data is treated as executable code rather than plain text, a classic manifestation of CWE-79 Improper Neutralization of Input During Web Page Generation commonly known as Cross-Site Scripting or XSS.
From a technical perspective, the vulnerability likely stems from the plugin's handling of attributes passed within the shortcode syntax. When a user with contributor privileges constructs a shortcode to embed a form, specific parameters such as titles, labels, or custom fields may be accepted without adequate filtering against script tags or event handlers like onerror or onload. Because WordPress typically restricts certain HTML tags for lower-privileged users to prevent basic XSS attacks, this vulnerability suggests that the plugin either bypasses these core sanitization filters by using a less restricted function such as wp_kses_post incorrectly or fails to encode output in contexts where special characters must be escaped. Consequently, an attacker can craft a malicious shortcode containing JavaScript payloads that execute when another user views the page containing the embedded form. This execution occurs within the browser of the victim, leveraging the trust relationship between the browser and the application hosting the vulnerable plugin.
The operational impact of this vulnerability is substantial because it facilitates stored or reflected cross-site scripting depending on how the data persists in the database. If the malicious shortcode content is saved to the post or page content, it becomes a persistent threat that affects every visitor who views the affected entry. Attackers can exploit this capability to steal session cookies, hijack administrative accounts if they trick an administrator into viewing the payload, deface websites by altering DOM elements, redirect users to phishing sites, or deploy further malware through drive-by downloads. The severity is amplified in environments where multiple contributors are active, as any contributor can introduce these payloads without needing higher-level access rights like editor or administrator roles. This lowers the barrier for entry significantly compared to vulnerabilities requiring admin privileges, making it a more prevalent risk in collaborative content management systems.
In terms of industry standard classification, this vulnerability aligns with CWE-79 and is often associated with ATT&CK technique T1059 Command and Scripting Interpreter under the Execution tactic when considering the broader impact of running arbitrary code within the user's context. It also touches upon CWE-601 URL Redirection to Untrusted Site which may be a secondary effect if the XSS payload redirects victims. The flaw highlights critical gaps in input validation strategies for plugins that interact with external services, emphasizing the need for strict adherence to secure coding practices such as output encoding and parameterized handling of dynamic content.
To mitigate this vulnerability, immediate action is required by updating the Wufoo Shortcode plugin to a version greater than 1.55 where these issues have been addressed by the developers through improved sanitization routines. Administrators should ensure that all plugins are kept up-to-date with their latest stable releases to patch known security flaws. Additionally, implementing a Web Application Firewall can provide an additional layer of defense by filtering out malicious payloads before they reach the application logic. For organizations relying on this plugin, it is advisable to review user roles and permissions to minimize the number of users with contributor access who can publish content containing shortcodes. Regular security audits and code reviews focusing on input validation for third-party integrations are essential preventive measures against similar XSS vulnerabilities in WordPress ecosystems.