The RSVPMaker plugin for WordPress is vulnerable to unauthenticated SQL Injection due to missing SQL escaping and parameterization on user supplied data passed to a SQL query in the rsvpmaker-api-endpoints.php file. This makes it possible for unauthenticated attackers to steal sensitive information from the database in versions up to and including 9.2.6.
The RSVPMaker Excel WordPress plugin is vulnerable to Reflected Cross-Site Scripting due to a reflected $_SERVER["PHP_SELF"] value in the ~/phpexcel/PHPExcel/Shared/JAMA/docs/download.php file which allows attackers to inject arbitrary web scripts, in versions up to and including 1.1.
The Import feature of the RSVPMaker WordPress plugin before 8.7.3 (/wp-admin/tools.php?page=rsvpmaker_export_screen) takes an URL input and calls curl on it, without first validating it to ensure it's a remote one. As a result, a high privilege user could use that feature to scan the internal network via a SSRF attack.