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 TwigLoaderString 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.

Deserialization of Untrusted Data vulnerability in supsystic Contact Form by Supsystic contact-form-by-supsystic allows Command Injection.This issue affects Contact Form by Supsystic: from n/a through <= 1.7.28.

The Contact Form by Supsystic plugin for WordPress is vulnerable to Stored Cross-Site Scripting via IP Address Header in all versions up to, and including, 1.10.2 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. An unauthenticated attacker can first call the 'updateNonce' action — which is accessible without authentication due to its absence from the plugin's permission list — to obtain a valid nonce, then submit a contact form with a malicious payload in a spoofed IP header such as X-Forwarded-For.

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in supsystic Contact Form by Supsystic contact-form-by-supsystic allows Reflected XSS.This issue affects Contact Form by Supsystic: from n/a through <= 1.7.36.

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in supsystic Contact Form by Supsystic contact-form-by-supsystic allows Stored XSS.This issue affects Contact Form by Supsystic: from n/a through <= 1.7.28.