Piotnet Forms <= 2.1.40 - Unauthenticated Arbitrary File Upload via Form File Upload
Strategic Overview
- Status
- Unpatched
- Affected Plugin
- Piotnet Forms
- Affected Version
<= 2.1.40- CVSS
- 9.8Critical
- Weakness type
- CWE-434 · Unrestricted Upload of File with Dangerous Type
- CVE
CVE-2026-4883
At a glance
CVE-2026-4883 is a critical-severity Unrestricted Upload of File with Dangerous Type vulnerability in the Piotnet Forms WordPress plugin, affecting versions <= 2.1.40. It carries a CVSS score of 9.8 (reachable over the network; low attack complexity; high confidentiality, integrity, availability impact). Exploitation requires no authentication. No fixed release has been reported yet; treat installations running this software as exposed. Disclosed May 2026, reported by 0xd4rk5id3.
Vulnerability Overview
The Piotnet Forms plugin for WordPress is vulnerable to arbitrary file upload due to missing file type validation in the 'piotnetforms_ajax_form_builder' function in all versions up to, and including, 2.1.40. The plugin uses an incomplete extension blacklist that only blocks php, phpt, php5, php7, and exe extensions, while allowing dangerous extensions such as .phar or .phtml to be uploaded. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected site's server which may make remote code execution possible. Note: The exploit can only be exploited if a file field is added to the form.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site, and no interaction from a victim user. A successful exploit has high impact on confidentiality, integrity, availability — full site compromise territory.
CWE-434: Unrestricted Upload of File with Dangerous Type
Piotnet Forms <= 2.1.40 carries this weakness at piotnetforms_ajax_form_builder, and reaching it takes no account at all. An unrestricted file upload lets a caller store a file whose type or destination the application does not properly constrain.
If an uploaded file lands anywhere the server will execute, the flaw becomes remote code execution and the site should be treated as fully compromised. No fixed build of this plugin is recorded for Piotnet Forms yet, so installs running <= 2.1.40 stay exposed until the vendor ships one.
Remediation
No known patch available. Please review the vulnerability's details in depth and employ mitigations based on your organization's risk tolerance. It may be best to uninstall the affected software and find a replacement.
How does WordSec protect against this?
Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. No patched version is recorded yet, which is the case where a filtering layer matters most, because there is nothing to update to.
- Firewall
- Scanner
- Login Security
External References
Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C