Executive brief
Gravity Forms, a widely-used form-building plugin for WordPress websites, contains a critical flaw that allows unauthenticated attackers to upload executable files to affected servers. The vulnerability exploits a validation bypass in hidden file upload fields, enabling attackers to achieve remote code execution on any publicly accessible form with a hidden file field. This could allow an attacker to take complete control of a WordPress site and its underlying server.
Technical details
The vulnerability exists in the upload_file function due to a mismatch between the field validation pipeline and the file persistence pipeline. Hidden file upload fields bypass extension validation, and rejected files retain their upload state, which is later passed to upload_file() without re-validation. An unauthenticated attacker can exploit this on any publicly accessible form containing a File Upload field with Visibility set to Hidden.
Affected products
- Gravity Forms Gravity Forms up to and including 3.1.0.4
Timeline
- 2026-09-19: disclosed: CVE-2026-84434 published
- 2026-09-17: patched: Fixed in version 3.1.2 per changelog