The Salon Booking System – Free Version plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 10.30.32. This is due to missing or incorrect nonce validation on the setCustomText function. This makes it possible for unauthenticated attackers to inject arbitrary PHP code into the web-accessible translate-constants.php file within the plugin directory, enabling remote code execution on the server via a forged request granted they can trick a site administrator into performing an action such as clicking on a link. sanitize_text_field() is applied to the POST 'value' parameter but does not neutralize the characters — single quotes, parentheses, semicolons, $, and [] — required to break out of the PHP string literal into which the value is interpolated before being written to disk via file_put_contents().