Open Redirect arises whenever you have input which you then use to redirect the user. Open Redirection Vulnerability happens when a web application accepts an untrusted input that could cause the web application to redirect the request to a URL contained within untrusted input.
An attacker could write a new URL within the application that causes a redirect to a malicious external domain. This vulnerability can be used to perform successful phishing attacks and more.
Updated to the latest version released by moodle.