External risk intelligence

Hash Form Unauthenticated Arbitrary File Upload Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 10.0)

CVE-2026-81780

The vulnerability exists in a WordPress plugin, which typically powers web applications directly exposed to the public internet to facilitate user interaction, form submissions, and data collection.

Unrestricted File Upload

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A critical security flaw has been identified in Hash Form, a type of technology used for managing online submissions. This vulnerability could potentially allow unauthorized access and manipulation of systems without any credentials being required. The primary concern at this stage is to determine if this specific technology is in use and assess the potential exposure.

Unauthenticated users can upload files.
It impacts web forms and user data.
Confirm relevance and potential exposure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending a specially crafted request to a web application using a vulnerable version of Hash Form. This could allow them to upload an arbitrary file to the server, potentially leading to further compromise.

No authentication required.
Uploading a malicious file.
Server compromise and data theft.

Live Threat

Current exploitation, exposure, and threat context

Unauthenticated attackers could upload arbitrary files to Hash Form when supported by the advisory. This could allow them to execute malicious code on the server, potentially leading to a full system compromise.

Arbitrary files on the server.
Via unauthenticated file upload.
Server compromise and code execution.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in Hash Form affects applications that process user-submitted data via forms, likely involving web application or platform teams responsible for the content management system and its plugins. The first practical step is to identify all instances of the affected plugin, confirm their accessibility from external networks, and determine their business criticality. Subsequently, coordinate with the platform or application owner to plan for remediation.

Platform or application owners should own this issue.
Verify all Hash Form installations and external reachability.
Plan coordinated remediation during a maintenance window.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is Hash Form?

Hash Form is a WordPress plugin designed to handle web-based data collection. Users typically rely on it to build contact forms, surveys, or registration pages where visitors submit information directly to a website. Because it integrates into WordPress sites, it acts as a gateway for processing incoming user files and inputs.

How would you describe the CVE-2026-81780 weakness?

This vulnerability is classified as an Unrestricted Upload of File with Dangerous Type (CWE-434). In plain English, the plugin fails to properly verify the types of files being submitted by users. This allows someone to bypass normal security checks and save files of their choosing directly onto the server, which can lead to unauthorized control over the affected system.

Do I need to be logged in to trigger this Hash Form bug?

No, authentication is not required to exploit this flaw. An attacker can trigger the issue simply by sending a specifically crafted request to the web application. Note that the vulnerability relates to the upload process itself; it does not depend on the attacker having prior access, existing user privileges, or interacting with other site features.

Is my site at higher risk if it uses Hash Form?

Yes, if your site is connected to the internet. According to Halo Surface Signal, this vulnerability is particularly relevant because Hash Form is a plugin meant for public web interaction. Because it is designed to be accessible to visitors, any instance reachable from the internet carries an increased risk of being targeted by unauthorized parties.

What is the first step to address this for my organization?

Begin by creating a comprehensive inventory of all WordPress instances running the Hash Form plugin. Once you have identified which sites use the affected software, verify whether those sites are exposed to the public internet. After mapping these installations, work with your application or platform owners to prioritize a maintenance window for remediation.

References

patchstack.com/database/wordpress/plugin/hash-form/vulnerability/wor…

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.