CVE-2026-1889 in Outgrow Plugin
Summary
by MITRE • 03/21/2026
The Outgrow plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'id' attribute of the 'outgrow' shortcode in all versions up to, and including, 2.1. This is 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 • 03/21/2026
The vulnerability identified as CVE-2026-1889 affects the Outgrow plugin for WordPress, a widely used tool for creating interactive content and forms. This security flaw exists in all versions up to and including 2.1, representing a critical risk to WordPress installations that utilize this plugin. The vulnerability manifests through the 'outgrow' shortcode where the 'id' attribute fails to properly sanitize user input, creating an avenue for malicious code injection. The issue specifically targets the plugin's handling of shortcode parameters, where insufficient validation allows attackers to bypass security measures that should prevent dangerous content from being stored in the system. This type of vulnerability falls under CWE-79 which describes Cross-Site Scripting (XSS) conditions where improperly sanitized input is directly reflected back to users without proper escaping mechanisms. The vulnerability's impact is particularly severe because it requires only contributor-level access or higher, meaning that users with relatively low privileges can exploit this weakness to compromise the entire WordPress installation.
The technical exploitation of this vulnerability occurs through the manipulation of the 'outgrow' shortcode's 'id' attribute, which serves as the entry point for malicious script injection. When an authenticated attacker with contributor privileges or higher creates or modifies content containing a specially crafted 'id' parameter, the plugin fails to properly escape or validate this input before storing it in the database. This stored malicious content then executes whenever any user accesses a page containing the vulnerable shortcode, creating a persistent cross-site scripting attack vector. The flaw demonstrates poor input validation practices and inadequate output escaping mechanisms that are fundamental requirements for preventing XSS vulnerabilities. According to ATT&CK framework category T1566, this vulnerability represents a technique for Initial Access through the exploitation of web application vulnerabilities, specifically targeting the execution of malicious code in the context of a user's browser session. The stored nature of this XSS means that the malicious scripts are permanently embedded in the system rather than requiring a single interaction to deliver the payload.
The operational impact of this vulnerability extends far beyond simple script execution, as it provides attackers with the ability to perform session hijacking, data theft, and further system compromise. Once an attacker successfully injects malicious code through this vulnerability, they can steal user sessions, access sensitive data, modify content, or redirect users to malicious websites. The low privilege requirement for exploitation makes this vulnerability particularly dangerous in multi-user environments where contributors may have access to content creation features. The vulnerability affects not only the immediate plugin functionality but also the broader WordPress security posture, as successful exploitation can lead to complete system compromise. Attackers can leverage this vulnerability to establish persistent access, create backdoors, or use the compromised system as a staging area for further attacks against other network resources. Organizations using this plugin are at risk of data breaches, reputational damage, and potential regulatory compliance violations, especially in environments where user data protection is paramount.
Mitigation strategies for CVE-2026-1889 should prioritize immediate patching of the Outgrow plugin to the latest version that addresses this vulnerability. System administrators should ensure that all users with contributor-level access or higher are properly monitored and that access controls are appropriately configured to limit the potential for exploitation. The implementation of proper input validation and output escaping mechanisms should be enforced across all shortcode parameters within WordPress plugins to prevent similar vulnerabilities from occurring. Security measures should include regular vulnerability scanning of WordPress installations and plugin ecosystems to identify and remediate such issues before they can be exploited. Additionally, organizations should implement Content Security Policy (CSP) headers to add an additional layer of protection against XSS attacks. Regular security audits of plugin code should be conducted to ensure compliance with security best practices and to identify potential vulnerabilities before they can be exploited by malicious actors. The remediation process should also include user education to ensure that contributors understand the risks associated with creating content that may be vulnerable to injection attacks, and that proper security protocols are followed when managing website content.