Summary
CVE-2026-15748 is a critical arbitrary file upload vulnerability (CWE-434) in the Forminator Forms plugin for WordPress, affecting all versions up to and including 1.56.1. The flaw allows unauthenticated attackers to upload executable PHP files, which can lead to remote code execution and full site takeover. The vulnerability carries a CVSS v3.1 base score of 9.8 (Critical).
Technical details
- Root cause: the plugin’s
handle_file_uploadfunction relies on a dangerous-extension blocklist that performs exact-key matching, which can be bypassed using pipe-alternative MIME type keys. - This weak validation is combined with a public form submission handler that accepts attacker-controlled upload field configuration, allowing an attacker to influence what is treated as an allowed file type.
- Trigger conditions: the targeted site must have a form that contains both a File Upload field and a Select field.
- Attack vector: network, no authentication or user interaction required — an attacker submits a crafted form request directly to the public-facing form endpoint.
- Impact: successful exploitation allows uploading executable files (e.g., PHP webshells) to the server, enabling remote code execution and complete compromise of the affected WordPress site.
Affected software
- Forminator Forms – Contact Form, Payment Form & Custom Form Builder (WordPress plugin by WPMU DEV): all versions up to and including 1.56.1
Severity
- CVSS v3.1 Base Score: 9.8 (Critical)
- Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Mitigation and recommended actions
- Immediate: Update Forminator Forms to version 1.56.2 or later, which addresses the file type validation flaw.
- If immediate patching is not possible: review any forms that combine a File Upload field with a Select field and disable or restrict them until patched; audit upload directories for unexpected or executable files (e.g.,
.php); ensure custom upload directories enforce execution restrictions (e.g., via.htaccessor web server configuration). - After patching: audit server logs and upload directories for signs of prior exploitation, and rotate credentials/secrets if compromise is suspected.
How IONIX identifies potentially affected assets
IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.
- Raw response body:
/wp-content/plugins/forminator/

