WPSyncSheets For Contact Form 7 <= 1.8.0 - Unauthenticated PHP Object Injection to Remote Code Execution via Untrusted CF7 Submission Field via maybe_unserialize()

The WPSyncSheets For Contact Form 7 – CF7 Google Sheets Connector & Save to Database plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 1.8.0 via the 'any non-system CF7 field (e.g., your-message)' parameter parameter. This is due to insufficient sanitization of CF7 submission field values before database storage and the absence of an allowed_classes restriction on maybe_unserialize() during admin retrieval. This makes it possible for unauthenticated attackers to execute code on the server. Successful exploitation of the remote code execution gadget chain requires that a Google Sheets access token be configured in the plugin (its primary advertised feature), as this triggers autoloading of the bundled Monolog 2.10.0 library whose classes form the exploitable gadget chain; however, the underlying PHP Object Injection occurs regardless.

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. None of that substitutes for the fix: WPSyncSheets For Contact Form 7 1.8.1 closes this, and updating the plugin is the step that ends it.

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