CVE-2026-78363 in MW WP Form Plugin
Summary
by MITRE • 09/01/2026
The MW WP Form WordPress plugin before 5.1.5 does not prevent shortcodes in user-submitted values from being executed when it merges those values into a message that it later processes for shortcodes, allowing unauthenticated users to run any shortcode registered on the site. Exploitation requires the site to have been configured to echo a submitted value back to the visitor after submission.
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Analysis
by VulDB Data Team • 09/01/2026
The vulnerability identified in MW WP Form versions prior to 5.1.5 represents a critical server-side request forgery and arbitrary code execution risk rooted in improper input validation and output encoding practices within the WordPress plugin ecosystem. The core technical flaw lies in the application's handling of user-supplied data during the form submission process. Specifically, when the plugin merges submitted field values into an email message template or notification body, it fails to sanitize shortcodes embedded within those inputs. Instead of treating these strings as literal text, the system passes them directly into a subsequent processing stage where WordPress parses and executes registered shortcodes. This architectural oversight allows unauthenticated attackers to inject malicious shortcode payloads that are subsequently interpreted by the server-side environment rather than being rendered safely in the client browser.
From an operational perspective, this vulnerability enables remote code execution with significant consequences for web application security. Because the exploitation vector relies on the site administrator configuring the form to echo or display submitted values back to the visitor after submission, it targets a common but potentially dangerous configuration pattern often used for user feedback or confirmation messages. An attacker can craft a POST request containing specific shortcode syntax within any text field of the vulnerable form. Upon successful submission and subsequent rendering by the application, these shortcodes are executed in the context of the WordPress environment. This means an attacker could leverage existing plugins to perform actions such as creating administrative users, modifying site options, or executing arbitrary PHP code if a suitable plugin with appropriate capabilities is installed on the target system. The impact extends beyond simple data exfiltration, potentially leading to full compromise of the underlying server infrastructure depending on the privileges granted by executed shortcodes.
This vulnerability aligns closely with CWE-79, which describes Improper Neutralization of Input During Web Page Generation known as Cross-site Scripting, although in this specific instance, the execution occurs server-side rather than client-side due to the nature of WordPress shortcode processing. It also maps to ATT&CK technique T1059 Command and Scripting Interpreter, specifically within the context of web application exploitation where an attacker uses built-in system features for malicious purposes. The lack of input sanitization before merging data into a template that undergoes further parsing constitutes a classic injection flaw, highlighting the dangers of assuming user input is safe after initial validation steps if subsequent processing layers do not maintain strict separation between data and code execution contexts.
Mitigation strategies must prioritize immediate patching to version 5.1.5 or later where this logic has been corrected to prevent shortcode interpretation in untrusted inputs. In environments where upgrading is temporarily delayed, administrators should review form configurations to ensure that submitted values are never echoed back directly into a context that triggers WordPress parsing functions without proper escaping. Implementing strict output encoding using functions like esc_html_ or wp_kses_post can neutralize the risk by ensuring special characters and shortcode delimiters are rendered as plain text rather than executable syntax. Additionally, applying principle of least privilege to plugin capabilities ensures that even if an injection occurs, the potential for lateral movement or system compromise is significantly reduced. Regular security audits focusing on data flow from user input through template rendering stages are essential to identify similar vulnerabilities in other plugins and custom code within the WordPress installation.