CRITICALVulnerability
Verified
Global
NVD Critical: CVE-2026-4257 — The Contact Form by Supsystic plugin for WordPress is vulnerable to Server-Side ...
Monday, March 30, 2026 at 10:16 PM UTC·Source: NIST NVD
Updated: Wednesday, April 1, 2026 at 07:13 PM UTC
Executive Summary
The Contact Form by Supsystic plugin for WordPress is vulnerable to Server-Side Template Injection (SSTI) leading to Remote Code Execution (RCE) in all versions up to, and including, 1.7.36. This is due to the plugin using the Twig `Twig_Loader_String` template engine without sandboxing, combined with the `cfsPreFill` prefill functionality that allows unauthenticated users to inject arbitrary Twig
Analysis
The Contact Form by Supsystic plugin for WordPress is vulnerable to Server-Side Template Injection (SSTI) leading to Remote Code Execution (RCE) in all versions up to, and including, 1.7.36. This is due to the plugin using the Twig `Twig_Loader_String` template engine without sandboxing, combined with the `cfsPreFill` prefill functionality that allows unauthenticated users to inject arbitrary Twig expressions into form field values via GET parameters. This makes it possible for unauthenticated attackers to execute arbitrary PHP functions and OS commands on the server by leveraging Twig's `registerUndefinedFilterCallback()` method to register arbitrary PHP callbacks.
CVSS Score: 9.8. Published: 2026-03-30T22:16:20.313.