CVE-2026-101335 in Forminator Forms Plugin
Summary
by MITRE • 10/16/2026
The Forminator Forms – Contact Form, Payment Form & Custom Form Builder plugin for WordPress is vulnerable to Arbitrary Shortcode Execution in versions up to, and including, 1.58.1. This is due to the forminator_replace_quiz_form_data() helper invoking do_shortcode() on the fully expanded notification body once the {quiz_result} merge tag has been substituted, while the earlier-substituted {user_agent} and {refer_url} merge tags carry unauthenticated attacker-controlled bytes (the User-Agent header and the referer_url POST parameter) through sanitize_text_field()/esc_html(), neither of which strip the '[' and ']' shortcode delimiters. This makes it possible for unauthenticated attackers to execute arbitrary WordPress shortcodes registered on the site by submitting a quiz whose notification template contains {quiz_result}; the resulting impact depends on the shortcodes exposed by other installed plugins/themes and can range from arbitrary content injection to information disclosure.
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Analysis
by VulDB Data Team • 10/16/2026
The Forminator Forms plugin for WordPress, specifically in versions up to 1.58.1, suffers from a critical Arbitrary Shortcode Execution vulnerability that stems from improper handling of user-supplied data during the processing of quiz form notifications. This flaw allows unauthenticated attackers to execute arbitrary shortcodes registered on the target WordPress site by manipulating specific merge tags within notification templates. The vulnerability is rooted in how the plugin processes dynamic content substitution, where certain fields are sanitized but fail to strip essential delimiters required for shortcode execution, thereby creating a code injection vector that bypasses standard security controls.
The technical mechanism of this exploit involves the helper function forminator_replace_quiz_form_data(), which is responsible for substituting merge tags with actual user input before sending notification emails or displaying results. When a quiz submission includes specific fields such as {user_agent} and {refer_url}, these values are derived directly from unauthenticated HTTP requests, specifically the User-Agent header and the referer URL POST parameter respectively. Although the plugin applies sanitization functions like sanitize_text_field() and esc_html() to these inputs, these functions do not remove square brackets '[' and ']'. Consequently, if an attacker crafts a malicious input containing shortcode syntax within these fields, the sanitized data retains its executable structure.
The critical failure occurs when the notification body is processed for the {quiz_result} merge tag substitution. At this stage, the plugin invokes WordPress's native do_shortcode() function on the fully expanded notification content. Because the previously substituted user_agent and refer_url values still contain unstripped square brackets, any shortcodes embedded within them are interpreted by WordPress as executable commands rather than plain text. This sequence of events allows an attacker to inject arbitrary shortcode payloads that will be executed in the context of the current logged-in user or potentially with elevated privileges depending on how the target site's theme and other plugins handle those specific shortcodes.
The operational impact of this vulnerability is significant and varies based on the ecosystem of installed plugins and themes. Attackers can leverage exposed shortcodes to achieve various malicious outcomes, ranging from arbitrary content injection into email notifications to severe information disclosure attacks. For instance, if a vulnerable plugin exposes shortcodes that retrieve database records or user metadata, an attacker could extract sensitive data such as administrator credentials, private messages, or configuration details. In more complex scenarios involving plugins with administrative capabilities exposed via shortcodes, the impact could escalate to remote code execution or complete site compromise, effectively turning a simple contact form into a powerful attack vector against the entire WordPress installation.
From a classification perspective, this vulnerability aligns with CWE-79, which covers Improper Neutralization of Input During Web Page Generation commonly known as Cross-Site Scripting (XSS), although in this context it manifests more severely as Arbitrary Code Execution via Shortcode Injection. It also relates to CWE-20, indicating improper input validation where the sanitization process is insufficient for the intended use case. In terms of offensive security frameworks like MITRE ATT&CK, this technique falls under T1190 Exploit Public-Facing Application and specifically leverages command injection principles adapted for WordPress shortcode contexts, allowing attackers to execute commands within the application's logic layer without direct shell access.
To mitigate this vulnerability, site administrators must immediately update the Forminator Forms plugin to version 1.58.2 or later, where the issue has been addressed by properly stripping shortcodes delimiters from user-supplied data before it is passed through do_shortcode(). Until an upgrade can be performed, implementing a Web Application Firewall (WAF) rule that blocks requests containing square brackets within form submission fields related to quiz results and notifications can provide temporary protection. Additionally, reviewing the site for any exposed shortcodes in installed plugins and disabling unnecessary ones reduces the attack surface available to potential exploiters. Regular security audits focusing on input sanitization practices in custom forms are also recommended to prevent similar issues arising from other third-party extensions or custom code implementations.