Joomla! Component Calendar Planner 1.0.1 contains an SQL injection vulnerability that allows unauthenticated attackers to inject SQL commands through the category_id parameter. Attackers can send GET requests to the events view with malicious SQL code in the category_id parameter to extract sensitive database information.
https://www.vulncheck.com/advisories/joomla-component-calendar-planner-sql-injection
https://extensions.joomla.org/extensions/extension/calendars-a-events/events/calendar-planner/