Description

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.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "4.8",
  "pubDate": "2026-09-01T08:17:01.510Z",
  "pubdate": "2026-09-01T08:17:01.510Z",
  "executiveSummary": "The MW WP Form plugin, in versions prior to 5.1.5, contains a critical security vulnerability involving improper neutralization of user-supplied data, specifically concerning shortcode execution.\nThe vulnerability allows unauthenticated attackers to leverage the WordPress shortcode parsing engine to execute arbitrary shortcodes registered within the site environment.\nThis flaw occurs because the plugin merges user-submitted form data into message strings that are subsequently processed by the WordPress shortcode handling mechanism without adequate sanitization or escaping.\nThe primary impact is the unauthorized execution of site-wide shortcodes, which may lead to sensitive information disclosure, unauthorized administrative actions, or secondary attacks depending on the capabilities of the shortcodes available in the installed plugin ecosystem.\nExploitation is contingent upon the specific site configuration where the plugin is instructed to echo or display submitted form values back to the user upon submission.\nGiven the potential for remote exploitation by unauthenticated actors, this vulnerability presents a significant risk to site integrity and data confidentiality, requiring immediate patching to version 5.1.5 or later.",
  "technicalDetails": "The root cause of this vulnerability lies in the insecure handling of user-supplied input during the form submission processing lifecycle. When a user submits data through an MW WP Form, the plugin processes the input and merges these values into a string meant for display or email generation. If these values are not properly sanitized or if the input contains WordPress shortcode syntax (e.g., [shortcode]), the subsequent rendering process triggers the WordPress do_shortcode() function or equivalent processing logic.\nThe WordPress shortcode API allows for the dynamic generation of content or the execution of server-side logic based on shortcode tags. By injecting these tags into a form field, an attacker can bypass standard input validation, as the application treats the malicious payload as legitimate content until the final rendering phase. The vulnerability is explicitly triggered when the site administrator configures the plugin to reflect submitted data back to the user, effectively turning a stored or reflected input vector into an execution context.\nThe attack flow follows a predictable sequence: First, an unauthenticated attacker identifies a form managed by the MW WP Form plugin. Second, the attacker crafts a malicious payload consisting of one or more WordPress shortcodes registered on the target site. Third, the attacker submits the form, inserting the shortcode payload into fields that are intended to be reflected back to the user. Finally, the application processes the form submission, merges the attacker's input into the message structure, and passes this structure to a function that processes shortcodes. The resulting execution occurs within the server's process space, potentially rendering restricted content, performing site-specific actions, or triggering server-side requests depending on the available shortcodes.\nThis vulnerability is classified as an improper neutralization of input during web page generation (Shortcode Injection). Because it does not require administrative or authenticated access to initiate, it is highly accessible for remote exploitation. The impact is dictated by the environment; if the site has installed plugins with high-privilege shortcodes (such as those for management, file access, or database queries), the attacker can leverage these to elevate their impact significantly beyond mere content manipulation.\nVersions prior to 5.1.5 are considered vulnerable. The lack of strict filtering of shortcode brackets or the direct passing of user input to the shortcode processor are the primary points of failure within the plugin's code logic."
}